Showing papers in "IEEE Transactions on Magnetics in 1980"
TL;DR: In this article, the magnetic head, the medium and the recording properties on a new perpendicular magnetic recording system are described. But the magnetic recording medium is not discussed. And the complemental features between the perpendicular and the longitudinal recording are discussed to establish an efficient magnetic recording systems.
Abstract: This paper describes the recent studies for the magnetic head, the medium and the recording properties on a new perpendicular magnetic recording system. The complemental features between the perpendicular and the longitudinal recording are discussed to establish an efficient magnetic recording system. Superior response in the amplitude and the peak shift characteristics for a digital signal proves that the perpendicular magnetization mode is basically free from the recording demagnetization in high densities and the maximum density has been limited merely by the resolution of the reproducing head. Significant improvement for the recording and the reproducing sensitivities of a perpendicular head has been made by using a composite anisotropy medium composed by double layers of Fe-Ni and Co-Cr thin films.
295 citations
TL;DR: In this paper, the dodecanoic (lauric) acid was used instead of dodecylamine as the dispersing agent, and the resulting aqueous magnetic fluid was found to be more stable toward dilution with water.
Abstract: As part of its program in advancing mineral technology, the Bureau of Mines, U.S. Department of the Interior, has investigated the production of water-base magnetic fluids that are stable toward dilution, and therefore fit for mineral and material beneficiation. Extension of the Bureau developed peptization technique for kerosine-base magnetic fluids to the preparation of the aqueous variety was possible when oleic acid was replaced by dodecylamine. The fluids thus prepared were, however, not stable toward dilution. Irreversible flocculation followed the addition of excessive quantities of water, such as would be encountered in mineral beneficiation operations. When dodecanoic (lauric) acid was used instead of dodecylamine as the dispersing agent, the resulting aqueous magnetic fluid was found to be more stable toward dilution with water. In this second generation water-base magnetic fluid, the dodecanate anionic dispersing agent is superior to the commonly used dodecylamine cationic dispersing agent. Chemisorption of dodecanate anion on the magnetite surface proper by chemically bonding to surface iron atoms is contrasted to the mere adsorption of a cationic surfactant on the solution side of the electric double layer. Expansion of the double layer by dilution and the accompanying decrease in dodecylamine bulk concentration can detach the cationic dispersing agent from the particles of old generation magnetic fluids and nullify their electrostatic charge. By contrast, the firmly held anionic dispersing agent will continue to adhere to the magnetic particles while augmenting their electrostatic charge. Thus, while the former fluids may irreversibly flocculate, the new generation fluids will resist flocculation upon dilution.
269 citations
TL;DR: In this article, a new method was developed to measure the saturation magnetostriction of a thin amorphous ribbon based on the use of small-angle magnetization rotation, which measured the change in anisotropy field caused by the tensile stress.
Abstract: A new method was developed to measure the saturation magnetostriction of a thin amorphous ribbon. It is based on the use of small-angle magnetization rotation to measure the change in anisotropy field caused by the tensile stress. Measurements have been performed on Metglas 2826, 2605, and Co-Si-B amorphous ribbons. The maximum experimental error of the measurement was estimated to be about ±5 percent. It is shown that the sensitivity of the method depends on the shape anisotropy field. The estimated sensitivity was about 2 × 10-7for Metglas 2826 ribbon with 1.8 mm × 40 μm × 12 cm in dimensions.
235 citations
TL;DR: Very fine particles of magnetite, nickel ferrite, and cobalt ferrite were produced by grinding coarser powders in a ball mill with a carrier fluid and a surfactant.
Abstract: Very fine particles of magnetite, nickel ferrite, and cobalt ferrite were produced by grinding coarser powders in a ball mill with a carrier fluid and a surfactant. The particles were examined by means of chemical analysis, electron microscopy, x-ray diffraction, magnetic measurements, and Mossbauer spectroscopy. Properties were determined before and after removing the surfactant coating. The most significant observation was that in some systems a large fraction of the spins was pinned in extremely high anisotropy fields as a result of bonding to the surfactant molecules. Anomalous magnetic hysteresis behavior was also noted when the surfactant coating was present.
160 citations
TL;DR: In this paper, a new type of cathode sputtering apparatus with two targets facing each other was developed to prepare magnetic films at a high deposition rate without the extreme rise of the substrate temperature.
Abstract: A new type of cathode sputtering apparatus with two targets facing each other has been developed to prepare magnetic films at a high deposition rate without the extreme rise of the substrate temperature. When two disks of iron and nickel were used as targets, the maximum deposition rates obtained were approximately 4000 and 5000 A/min, respectively. The substrate temperature was not elevated above 200°C during sputtering. The high rate deposition of Mo permalloy films also was attempted by co-sputtering of two facing targets composed of disks of iron and nickel and chips of molybdenum. The Vicker's hardness of the obtained Mo permalloy films was about 900 and the typical values of permeability at 1 MHz magnetic field and coercive force at dc magnetic field of them were about 2500 and 0.16 Oe, respectively.
159 citations
TL;DR: In this article, the optical birefringence and dichroism observed in magnetic fluids when subjected to a magnetic field are generally attributed to orientation of the particles, to anisotropic spatial ordering, or to string formation.
Abstract: The optical birefringence and dichroism observed in magnetic fluids when subjected to a magnetic field are generally ascribed to orientation of the particles, to anisotropic spatial ordering, or to string formation. Magnitude, concentration- and time dependence of the anisotropies predicted by these mechanisms are compared with the available experimental data. This leads to the conclusion that orientation of small aggregates and secondary aggregation of large aggregates into strings are the most likely cause of the large anisotropies. Orientation of single particles can be responsible for small anisotropies only. Field-induced spatial ordering has, at least optically, not (yet) been observed.
138 citations
TL;DR: In this article, the authors used the Bitter technique to observe magnetization distribution in the Co-Cr medium, and the transition of magnetization was directly observed on the top and bottom surfaces of the film.
Abstract: The extremely high resolution properties in a perpendicular magnetic recording system were studied with a recently developed Co-Cr film medium. Bitter technique was used to observe magnetization distribution in the medium, and the transition of magnetization was directly observed on the top and the bottom surfaces of the film. It was proved that an ideal perpendicular magnetization mode, having a very narrow transition width, takes place even in a high recording density over 40 kBPI. From the angular variation of H c and the micro-structure of the Co-Cr film, it was concluded that the high recording resolution of the film results from the fine columnar particles which show the rotational mechanism of magnetization reversal accompanied by a perpendicular magnetocrystalline anisotropy. The Co-Cr film was also found to be superior in perpendicular anisotropy to any other Co-M films studied here in.
116 citations
116 citations
TL;DR: In this paper, a simple mathematical formalism for describing arbitrary hysteresis processes is presented, and the information required to apply this formalism to a given magnetic material can be obtained with relatively little effort from experimental hystresis curves such as normal loops or in special cases, from just the initial curve.
Abstract: A simple mathematical formalism for describing arbitrary hysteresis processes is presented. The information required to apply this formalism to a given magnetic material can be obtained with relatively little effort from experimental hysteresis curves such as normal loops or, in special cases, from just the initial curve. The basic physical model is that of Preisach. A more convenient, less widely known, treatment of this modes by Everett to which we have applied magnetic symmetry constraints leads to a succinct description of hysteresis processes. We have applied this procedure to calculate losses in nonoriented electrical steel laminations. The fully non-linear electromagnetic field equations were solved on the computer for this simple geometry with no restrictions on the hysteresis paths. The calculated losses agreed at the 5% level with experimental losses for a wide range of frequencies and inductions.
100 citations
TL;DR: In this paper, the authors describe and discuss the construction of sink-float separators using permanent magnets and provide test results for artificial mixtures of nonferrous metals, including aluminum, copper, zinc and lead.
Abstract: The development of sink-float separators for materials of different densities, which utilize the levitation force of magnetic fluid, have been recently reported. The system usually consists of an electromagnet, separation cell, equipment for recovery of magnetic fluid smeared on the separated products, and controlling system. This paper describes and discusses the construction of sink-float separators using permanent magnets and provides test results for artificial mixtures of nonferrous metals. Ferrite magnet and rare-earth cobalt magnet were used as magnetic field generators in two separators. One for separating aluminum from other nonmagnetic metals, and the other to separate copper, zinc and lead from each other. A series of tests were performed on samples of 6 to 30 mm size, and it was found that the separators operated as expected. The separation of finer metals, however, proved difficult due to the attractive force which acts between nonmagnetic bodies immersed in magnetic fluid in a magnetic field. The chemical process to recover the magnetic fluid from smeared separation products is also proposed.
89 citations
TL;DR: A detailed investigation on the thermal expansion, magnetic properties and electrical resistance of rapidly quenched amorphous (Fe,Co,Ni)-Zr alloys has been undertaken in this article.
Abstract: A detailed investigation on the thermal expansion, magnetic properties and electrical resistance of rapidly quenched amorphous (Fe,Co,Ni)-Zr alloys has been undertaken. Magnetic properties of these alloys are reported separately in this conference. The thermal expansion curves exhibit typical invar characteristics below the Curie temperature due to positive spontaneous volume magnetostriction us similar to those for Fe-Ni crystalline invar alloys. The reduced magnetization decreases strongly with increasing temperature being analogous to the case of other amorphous invar alloys. Moreover, w s at 0 K and electrical resistance at room temperature and Liq. N 2 temperature increase in the invar region. Amorphous ternary alloys of (Fe,Co, Ni) 90 Zr 10 with about 72 at% Fe have the invar characteristics in a wide temperature range and in this composition range, the volume magnetostriction and electrical resistance show maximum values of about 1.5 × 10-2and 160 μΩcm respectively.
IBM1
TL;DR: In this article, a comparison of perpendicular and longitudinal recording indicates that conventional heads are suitable for recording on high coercivity media having perpendicular magnetic anisotropy, at equal bit shift and head to disk separation perpendicular recording gives a factor of 2.5 increase in the linear density attained with media in use today.
Abstract: A comparison of perpendicular and longitudinal recording indicates that conventional heads are suitable for recording on high coercivity media having perpendicular magnetic anisotropy. At equal bit shift and head to disk separation perpendicular recording gives a factor of 2.5 increase in the linear density attained with media in use today.
TL;DR: In this article, the vector potential and magnetic field of a conic cylinder segment of arbitrary azimuthal and axial length, and carrying a constant peripheral current, were derived.
Abstract: Analytical expressions for the components of the vector potential and magnetic field of a thin circular conic cylinder segment of arbitrary azimuthal and axial length, and carrying a constant peripheral current are derived. All the expressions developed consist of known functions such as Jacobian elliptic functions, and complete and incomplete elliptic integrals of the first, second, and third kind and thus permit a new time-saving efficient computation algorithm.
TL;DR: In this article, the magnetic properties of melt-quenched amorphous ribbons having the general composition TM 100-x Zr x (TM= Fe,Co and/or Ni) have been investigated.
Abstract: Magnetic properties of melt-quenched amorphous ribbons having the general composition TM 100-x Zr x (TM= Fe,Co and/or Ni) have been investigated. Composition dependence of Curie temperature, Tc and magnetic moment, n B in Co 100-x Zr x and Ni 100-x Zr x alloys is similar to Co- and Ni-metalloid amorphous alloys. However, the decrement of Zr content in the Fe 100-x Zr x alloys causes both Tc and n B to decrease, and n B extrapolates at x=0 to almost 0 μ B . Such an unusual behavior of Tc and n B is also found on the Fe-rich portion of (Fe-Co-Ni) 90 - Zr 10 ternary system and Tc and n B of the Fe 90 Zr 10 alloy are 243 K and 1.29 μ B /Fe atom, respectively. For the Co 90 Zr 10 alloy the value of longitudinal linear magnetostriction λ is +3 × 10-6, and the zero-magnetostrictive composition lies near (Co .88 Ni .12 ) 90 Zr 10 and shifts to Fe-rich side with increasing Ni content.
TL;DR: In this paper, a magnetic liquid film sheared between a moving and stationary component forms the basis of these devices and the fluid is retained by magnetic forces and does not leak out.
Abstract: Applications of magnetic liquid technology to damping phenomenon are reviewed. Products utilizing ferrofluids, such as a rotary viscous inertia damper, linear damper, damper/seal assembly, and dashpot are discussed. The rotary dampers are used to enhance stepper motor performance. A magnetic liquid film sheared between a moving and stationary component forms the basis of these devices. The fluid is retained by magnetic forces and does not leak out. Examples of actual use of these dampers on operating systems, along with the test results, are presented.
TL;DR: In this article, it was found that small deposits of the mineral magnetite have been found in two regions of the pigeon's head and it is conceivable that this material may somehow be involved in the pigeons sensitivity to magnetic fields.
Abstract: Homing pigeons appear to use both a "map" and "compass" system to find their way home. Under sunny skies, the sun is used as a compass. But when the sun is obscured, pigeons appear to use the earth's magnetic field. The sensory basis of the pigeon's map is unknown but the disorientation of pigeons at magnetic anomalies under sunny conditions suggests that the map may be partly based on magnetic cues. Recently small deposits of the mineral magnetite have been found in two regions of the pigeon's head. It is conceivable that this material may somehow be involved in the pigeon's sensitivity to magnetic fields.
TL;DR: By rapid quenching techniques silicon-iron ribbons in polycrystalline state containing silicon in a range from 3.8 to 9.3 wt-percent were prepared as discussed by the authors.
Abstract: By rapid quenching techniques silicon-iron ribbons in polycrystalline state containing silicon in a range from 3.8 to 9.3 wt-percent were prepared. The speed for making ribbons was about 50m/s. The ribbons obtained were 20 to 150 μm in thickness, 2 to 25 mm in width, and 5 to 10 m in length. These ribbons were flexible and easily cold rolled. The grain size in the as-prepared ribbon was about 10 μm on the ribbon surface, and after annealing the grains grew to about 200 μm and a columnar structure perpendicular to the ribbon plane with grains extending through the entire thickness of the ribbon was observed. The coercive field in a straight ribbon 20 μm in thickness of composition 6.5Si-93.5Fe was 80 mOe after annealing at 1200°C for 35 minutes.
TL;DR: In this article, a three dimensional finite element formulation and algorithm for the solution of 3D magnetic fields was developed with applications to determination of local flux densities in a 3D field pattern, as well as global energy calculations of an air cored coil.
Abstract: A three dimensional finite element formulation and algorithm for the solution of 3-d magnetic fields was developed. The method is presented here with applications to determination of local flux densities in a 3-d field pattern, as well as global energy calculations of an air cored coil. The results compare well with closed form solution results. Experimental test data of the coil inductance is in agreement with finite element results. The development represents a new technique which is a potentially very powerful tool in many practical applications.
TL;DR: In this paper, it was shown that a minimum energy occurs when the stripe buckles with a buckling wavelength approximately equal to the width of the stripe, leading to the formation of walls perpendicular to the stripe.
Abstract: The coercivity of narrow stripes of 81 percent Ni-19 percent Fe films has been found to increase rapidly, by up to an order of magnitude, as the stripe width decreases and approaches 1 μm. Furthermore, the coercivity increases with decreasing film thickness as it does in sheet films, but in the stripes the changes in coercivity with film thickness are much larger than in sheet films. For example, in stripes of 2 μm × 100 μm, H c increases from 10 Oe to 35 Oe as the thickness decreases from 1800 A to 300 A. The increase in coercivity with decreasing stripe width may be explained by a buckling of the magnetization perpendicular to the length of the stripe. This buckling process was made visible by decoration of domain walls with Ferrofluid, and is shown to lead to the formation of walls perpendicular to the stripe. These walls do not move, but block reverse domains from propagating down the stripe. In the narrowest stripes (2 μm) fields larger than 100 Oe are required to collapse the 360° wall segments which eventually form. A theoretical model for this buckling process is given which shows that a minimum in energy occurs when the stripe buckles with a buckling wavelength approximately equal to the width of the stripe. These findings suggest that, as structures of NiFe like those in magnetic bubble devices and in magnetic recording heads are made smaller, coercivity and dispersion will rise significantly, leading in many cases to undesirable magnetic behavior.
TL;DR: In this article, the acoustic emission (AE) technique is applied to the detection of slider-to-disk contact, which can be used to measure the projection height distribution over an entire disk surface, one of the most important factors governing the reliability of disk files.
Abstract: Acoustic Emission (AE) technique is applied to the detection of slider-to-disk contact. The type of slider-to-disk contact is identified by detecting the AE caused by contact. Advantages of this method are simplicity of measurement and the ability to detect contact between slider and disk fabricated from any material. In addition, this method can be used to measure the projection height distribution over an entire disk surface, which is one of the most important factors governing the reliability of disk files.
TL;DR: In this article, a general set of relations for perturbation field and flow interfacial variables defined for a "prototype" magnetizable fluid layer is developed for describing the small signal stability characteristics of layered fluid systems, and experimental results of the most unstable wavelength in a Hele-Shaw cell are shown to agree well with theory.
Abstract: Recent work has shown that the fingering instability, which develops when a more viscous fluid is pushed through the voids of a porous medium or through a Hele-Shaw cell by a less viscous fluid, can be prevented if a magnetic field is applied tangential to a flat fluid interface separating magnetizable and non-magnetizable fluids. This earlier work is extended here by considering equilibrium magnetic field components both perpendicular and parallel to the flat interface. The tangential field component stabilizes those waves traveling along the field lines while the normal field is destabilizing. The analysis is developed through a general set of relations for perturbation field and flow interfacial variables defined for a "prototype" magnetizable fluid layer which can be used to describe the small signal stability characteristics of layered fluid systems. In a uniform tangential magnetic field geometry, experimental results of the most unstable wavelength in a Hele-Shaw cell are shown to agree well with theory.
TL;DR: In this article, a new preparation process for sputtered γ-Fe 2 O 3 thin film disks was developed, which is composed of Fe 3 O 4 film formation by reactive sputtering and oxidation.
Abstract: A new preparation process for sputtered γ-Fe 2 O 3 thin film disks has been developed. The new process is composed of Fe 3 O 4 film formation by reactive sputtering and oxidation to γ-Fe 2 O 3 film. The characteristic of the process is that the Fe 3 O 4 single phase film is formed directly by reactive sputtering of an Fe-alloy target in Ar-O 2 atmosphere. The magnetic properties and recording results of the newly developed γ-Fe 2 O 3 thin films were almost equal to those of the reported sputtered films. Recording density D 50 reached 1,100 bits/mm.
TL;DR: In this paper, the shape of the miscibility gap is not parabolic but of a peculiar shape, protruding to the Fe side along the Curie temperature, and the part of the protrusion is called the ridge.
Abstract: The miscibility gap of an Fe-Cr-Co system is further examined by monitoring the microstructures and the magnetic properties of the alloys. It is shown that the shape of the miscibility gap is not parabolic but of a peculiar shape, protruding to the Fe side along the Curie temperature. The part of the protrusion of the miscibility gap is called the "ridge" because of its shape resemblance. It is demonstrated that the alloys in the ridge region can exhibit very good magnetic properties. An Fe-25%Cr-12%Co alloy gives the magnetic properties as Br = 1.45 T(14.5 kG), bHc = 50.1 kA/m (630 Oe) and (BH)max = 61.3 kJ/m3(7.7 MG . Oe), which are almost comparable to those of the columnar Alnico 5 magnets.
TL;DR: The literature and patent search, with a few exceptions, covers material written or issued during the period from 1960 to mid-1979 as discussed by the authors, with the exception of a few exception.
Abstract: s (INSPEC), 1969-1979; Predicasts' Market Abstracts (PROMT), 1972-1979; Magazine Index, 1978-1979; and Government Reports (NTIS), 1964-1979. Other material was found through the use of the printed indexes: Chemical Abstracts, Physics Abstracts, Engineering Index, and Applieds, Physics Abstracts, Engineering Index, and Applied Science and Technology Index. The literature and patent search, with a few exceptions, covers material written or issued during the period from 1960 to mid-1979.
TL;DR: A novel SQUID biomagnetic susceptometer is described in this paper consisting of a second-order gradiometer combined with a superconducting field coil assembly, and the first clinical noninvasive diagnosis of liver iron overload achieved with this susceptometer at the Metropolitan General Hospital in Cleveland.
Abstract: This paper provides a review of the principles and practice of biomagnetic susceptometry, with particular reference to magnetic susceptibility measurements of the human liver. A novel SQUID biomagnetic susceptometer is described consisting of a second-order gradiometer combined with a superconducting field coil assembly. We report the first clinical non-invasive diagnosis of liver iron overload achieved with this susceptometer at the Metropolitan General Hospital in Cleveland. Estimates are provided for the limiting resolution of the method. Ongoing efforts to apply the same principles to the determination of iron overload in the heart are briefly described. Our work represents the first clinical diagnostic procedure to utilize the recently developed superconducting technology of weak field measurement.
TL;DR: Amorphous Tb x Fe 1-x (0.16 ) thin films produced by rf co-sputtering have been investigated for magneto-optic memory media application.
Abstract: Amorphous Tb x Fe 1-x ( 0.16 ) thin films produced by rf co-sputtering have been investigated for magneto-optic memory media application. The anisotropy, hysteresis and coercivity of the films were investigated as a function of composition and film thickness. The sputtered films were overcoated with thermally evaporated SiO. The effect of SiO thickness on the Kerr magneto-optic enhancement and the reflectivity was also measured. It was found that the magnetization and coercivity of those films having perpendicular anisotropy change dramatically not only with target composition but also with film thickness. Thin films having a high hysteresis loop squareness and a coercivity appropriate for magneto-optic recording (500 to 2000 Oe.) were produced from film compositions near the compensation composition of 22.3 at. % Tb. Thermomagnetic writing and reading of the TbFe films were made with a GaAs laser. The results show that the films have a high writing sensitivity (threshold energy of 0.2 nJ and saturation energy of 0.3 nJ) and a high reading contrast for bit sizes of 1 micron.
TL;DR: In this paper, the electric susceptibility of samples of ferrofluids subjected to a uniform magnetic field H was measured and interpreted as a magneto-electric directive effect, based on the assumption that the magnetic particles are roughly ellipsoidal and conducting grains.
Abstract: The electric susceptibility of samples of ferrofluids subjected to a uniform magnetic field H was measured. The electric susceptibility \chi is dependent on the magnitude of the magnetic field and on the relative direction between the electric field E and the magnetic field H . 1) When E is perpendicular to H, \frac{\partial\chi_{\perp}}{\partialH} 2) When E is parallel to H, \frac{\partial\chi_{\parellel}}{\partialH} > 0 These results have been interpreted as a magneto-electric directive effect. A model is proposed, based on the assumption that the magnetic particles are roughly ellipsoidal and conducting grains.
TL;DR: In this paper, a low-cobalt, ternary Fe-28Cr-10.5Co isotropic magnet alloy (Chromindur II), developed for use in the telephone receiver, is described.
Abstract: The processing, structure, and properties of a low-cobalt, ternary Fe-28Cr-10.5Co isotropic magnet alloy (Chromindur II), developed for use in the telephone receiver, are described. The new alloy is easy to process, and permits a convenient low-temperature recrystallization anneal of heavily cold rolled strips leading to a fine-grained, ductile, single-phase structure suitable for cold forming into the desired magnet shape prior to aging. Optimization of the microstructural control process during spinodal decomposition is discussed with a particular emphasis on solving the problem of critical control during aging required for desirable magnetic properties. It is shown that, in order to reproducibly achieve an optimum combination of wavelength and amplitude during decomposition, two drastically different continuous cooling curves, connected at some intermediate temperature, must exist. This newly devised, two-stage aging technique permits a reasonably wide heat treating window, and accomodates heat-to-heat compositional variations. Satisfactory isotropic magnet properties are reproducibly obtained by industrial heat treatment leading to a successful commercial application of the new alloy in the ring armature type telephone receiver.
TL;DR: In this paper, a finite element model was proposed to predict the apparent changes in the normalized complex impedance of a differential eddy current probe in axisymmetric NDT configurations.
Abstract: Development of computer based defect characterization schemes in quantitative eddy current nondestructive testing (NDT) requires an adequate mathematical model capable of describing the complicated interactions between the impressed and induced currents, primary and secondary fields and the flaws in materials. This paper describes a finite element model which predicts the apparent changes in the normalized complex impedance of a differential eddy current probe in axisymmetric NDT configurations. Using this 'numerical model' differential eddy current probe, signal trajectories (as obtained on an eddy-scope screen in actual testing) are predicted for three axisymmetric geometries associated with nuclear power plant steam generators - circumferential I.D. and O.D. slots in an INCONEL tube, and a carbon steel support plate encircling a defect-free tube. Comparison is made between the theoretical and experimental results at a probe excitation frequency of 100kHz. Finite element analysis techniques appear to be well suited to the modeling of eddy current NDT phenomena and for predicting the eddy current probe signal trajectories.
TL;DR: In this paper, a commercial magnetic recording tape was experimentally investigated, and it was found that the primary mechanism of tape aging and degradation resulted from hydrolysis of its polyester urethane binder.
Abstract: Almost all commercial magnetic recording tapes are manufactured employing a polyester urethane elastomer as the oxide binder and also as the backcoat binder on backcoated tapes. For temperature excursions encountered for ordinary tape use and storage, polyester urethanes as a general class of materials are typically susceptible to environmental degradation by hydrolysis: a chemical reaction between these materials and atmospheric water vapor. Extensive hydrolytic degradation can lead to the generation of sticky and gummy chemical products. It can be anticipated that a substantial contribution to environmental tape aging and performance characteristics might derive from the chemical behavior of ester hydrolysis. The environmental aging of a commercial magnetic recording tape was experimentally investigated, and it was found that the primary mechanism of tape aging and degradation resulted from hydrolysis of its polyester urethane binder. The chemical reaction is additionally reversible, a property which suggests a methodology for restoring and rejuvenating environmentally degraded tapes. Being a reversible reaction, there exists environmental conditions of relative humidity and temperatures which are ideal for long-term archival preservation. For the tape of this study, 24-percent relative humidity (RH) at room temperature was identified as its ideal storage humidity. This study may have significance for many industrial and government specifications which call out assorted qualifying tests involving tape exposure or tape operations at extremes of humidity and temperature. It is suggested from the findings of this work that such tests may measure and monitor the various manifestations of hydrolysis, which may bear little if any relationship to tape use at moderate ambient conditions or in hermetic environments. The results of this work further indicate that hermetic sealing of a tape may allow operations to higher temperatures than possible in air, with the upper temperature limit determined by lubricant boil-out or thermal degradation (pyrolysis) of the polymers.