Showing papers on "Saturation (magnetic) published in 1976"
TL;DR: In this paper, the electron-donor effects of boron and phosphorus are clearly seen for the first time; each atom of these metalloids gives ∼1.6 and 2.4 electrons, respectively, to the TM d bands.
Abstract: Continuously cast metallic glasses [METGLASR (trademark of the Allied Chemical Corporation) alloys] based on the transition metals (TM) iron, cobalt, and nickel can now be synthesized containing boron as the only metalloid. The different electron‐donor effects of boron and phosphorus are clearly seen for the first time; each atom of these metalloids gives ∼1.6 and 2.4 electrons, respectively, to the TM d bands. Extrapolation of the available magnetic moment data suggests a nonzero moment on nickel in (TM)80B20 glasses. The boron‐containing metallic glasses generally show higher Curie temperatures and room‐temperature saturation magnetizations than mixed‐metalloid glassy alloys of the same TM content.
161 citations
TL;DR: In this paper, synthetic titanomagnetites (1−x)Fe3O4, -xFe2TiO4 and 0 ≤ × × ≤ 0.6) were prepared by the ceramic oxide method and the equilibrium atmosphere method, and two size fractions were separated out.
Abstract: Synthetic titanomagnetites ((1−x)Fe3O4, - xFe2TiO4, 0 ≤ × ≤ 0.6) were prepared by the ceramic oxide method and the equilibrium atmosphere method, and two size fractions were separated out. The first contained particles of size >150 μm, while the second, which was ground in a water slurry, had a mean particle size of about 0.1μm. The magnetic hysteresis properties, i.e., coercive force HC, remanent coercive force ERC, saturation remanence JRS, JRS/JS, and initial susceptibility x0, were measured at room temperature. The coarse grain samples were found to be magnetically soft (HC ∼ 30 Oe) and the hysteretic properties independent of composition. In contrast, the fine grain samples were extremely hard (HC ∼ 400–2000 Oe) and their magnetic characteristics strongly dependent on composition. When compared with the Stoner-Wohlfarth model for single-domain magnetization, the agreement was good, indicating that these latter samples contain mainly single-domain grains. Samples containing both hard and soft fractions exhibited hysteretic properties that depended on the relative proportions of each size fraction.
105 citations
TL;DR: Saturation magnetizations and magnetic anisotropy constants for a series of amorphous GdCo films prepared by thermal evaporation were determined by means of ferromagnetic resonance and a force balance magnetometer.
Abstract: Saturation magnetizations and magnetic anisotropy constants were determined for a series of amorphous GdCo films prepared by thermal evaporation. The films covered the composition range from Gd0.05Co0.95 to Gd0.40Co0.60 and were studied by means of ferromagnetic resonance and a force balance magnetometer. The films, in contrast to those prepared by sputtering, had a hard perpendicular direction of magnetization when Co was less than 91 at.%, and easy and moderate directions within the plane of the film. The anisotropy constant can be expressed in terms of sublattice magnetizations by Ku=0.660MCo2 +2.218MCoMGd+0.097MGd2. The results are explained based on a pair‐ordering mechanism. The composition and temperature dependence of saturation magnetization is essentially the same in evaporated and sputtered films.
99 citations
TL;DR: In this paper, the authors investigated spectral changes induced by high-power CO 2 laser radiation in the direct intervalence band absorption of p-type germanium using a model of inhomogeneously broadened two-level systems.
Abstract: We investigate spectral changes induced by high-power CO 2 laser radiation in the direct intervalence band absorption of p-type germanium. Using a model of inhomogeneously broadened two-level systems, we deduce a room-temperature saturation intensity of 4 MW/ cm2from published observations of saturation of this absorption. The applicability of the two-level model to transitions between two electronic bands is discussed. We relate the linear absorption coefficient to the saturation intensity and the effective population difference, where the latter is obtained in a spherical band approximation. The result yields a value of 0.55 ps for the geometric mean of the phase and energy relaxation times. The meaning of these times is explained for our system, and quantitative agreement is found with published data on optical and acoustical lattice scattering probabilities. Specifically, we find a very short phase relaxation time of 0.09 ps. This allows the prediction of a burnt-hole spectral width of 57 cm-1(HWHM) at small saturation. In a preliminary experiment, we have observed the modulation of a CW CO2laser beam by intense nanosecond pulses of a second CO2laser offset in frequency by up to 140 cm-1.
60 citations
01 Jan 1976
TL;DR: In this article, it was shown that boron donates less electrons to the d−band of transition metal atoms compared with other glass-forming metalloids such as phosphorous.
Abstract: Recent developments in transition metal glasses have resulted in the synthesis of an iron‐rich glass (nominal composition, Fe80B20) in continuous ribbon form. The as‐quenched glass shows a saturation moment of 1.99 μB/Fe atom at 4.2 K, an induction of 16 kG at 300 K, a ferromagnetic Curie temperature of 650 K, a saturation magnetostriction of 30 × 10−6 and a coercivity Hc of about 100 mOe. Large domains, elongated parallel to the ribbon axis, are observed. Both Mossbauer and FMR data indicate that the magnetic anisotropy (K = 3 × 104 erg/cm3) is in the ribbon plane. Evidence is presented that boron donates less electrons to the d‐band of transition metal atoms compared with other glass‐forming metalloids such as phosphorous. Some of the low‐field properties include: the permeability at 20 G, μ(20) = 1,700, μmax = 102,000 and core‐loss, W ≃ 0.3 to 0.4 watts/kg at f=1 kHz and Bmax = 1 kG. Field annealing results in improvements in these properties: A typical field‐annealed toroid shows Hc∼40 mOe, μ(20) = 4,...
57 citations
TL;DR: In this paper, the saturation moment and Curie temperature of YCo5xNi5−5x was determined for compounds of the type YCo 5xNi 5−5X.
Abstract: For compounds of the type YCo5xNi5−5x the saturation moment and Curie temperature were determined. For large Co concentrations the rigid‐band approach applies. The magnetic splitting of the 3d band collapses near x=0.2. Magnetic isotherms were studied at 4.2 K as a function of concentration. The form of the virgin magnetization curve, the presence of large intrinsic coercive forces, and the observation of pronounced thermomagnetic history effects suggest the presence of narrow Bloch walls of only a few interatomic distances in these compounds. It is argued that the presence of narrow Bloch walls is the primary reason for the high coercive forces observed usually in solid pieces of materials of the type RCo5xCu5−5x.
54 citations
TL;DR: In this article, the magnetic properties of RMg3 compounds were investigated by X-ray diffraction; the corresponding powder diffractograms were indexed according to the cubic Fe3Al type-structure.
Abstract: The RMg3 compounds (R = La, Ce, Pr, Nd, Sm, Gd, Tb) were investigated by X-ray diffraction; the corresponding powder diffractograms were indexed according to the cubic Fe3Al type-structure. The magnetic properties of these compounds were studied in the range 4–300 K, with magnetic field strengths up to 18 kOe. The asymptotic Curie temperature was found to be negative for CeMg3, PrMg3 and NdMg3 but positive for GdMg3 and TbMg3. The compound SmMg3 proved to have a Neel temperature TN = 6.5 K, but no magnetic ordering was detected in CeMg3, PrMg3 and NdMg3. The compounds GdMg3 and TbMg3 apparently order ferromagnetically. The much-too-low saturation moments for these compounds are an indication, however, of a more complex magnetic structure. The observed magnetic properties are in disagreement with an RKKY type description. It is suggested that 5d electrons may have some influence on the coupling between the rare-earth moments.
53 citations
TL;DR: In this paper, the domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique using the magnetic powder pattern technique was investigated using two different types of domains (a maze domain and a 180°-domain) observed on the specimen surface.
Abstract: The domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique was investigated using the magnetic powder pattern technique. Two different types of domains (a maze domain and a 180°-domain) were observed on the specimen surface. The relationship between the domain structure and the magnetization process was also investigated. The results showed that some of the 180°-walls, which ran nearly parallel to the long axis of the ribbon, caused the hysteresis in the magnetization curve, while the maze domain was responsible for the difficulty in obtaining the saturation in magnetization. The maze domain arises probably from the uniaxial magnetic anisotropy having the direction of easy magnetization perpendicular to the surface. This anisotropy seems to be caused by the magnetoelastic coupling between positive magnetostriction and internal stress in the specimen.
51 citations
Journal Article•
01 Jan 1976-Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
TL;DR: In this paper, the domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique using the magnetic powder pattern technique was investigated using two different types of domains (a maze domain and a 180°-domain) observed on the specimen surface.
Abstract: The domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique was investigated using the magnetic powder pattern technique. Two different types of domains (a maze domain and a 180°-domain) were observed on the specimen surface. The relationship between the domain structure and the magnetization process was also investigated. The results showed that some of the 180°-walls, which ran nearly parallel to the long axis of the ribbon, caused the hysteresis in the magnetization curve, while the maze domain was responsible for the difficulty in obtaining the saturation in magnetization. The maze domain arises probably from the uniaxial magnetic anisotropy having the direction of easy magnetization perpendicular to the surface. This anisotropy seems to be caused by the magnetoelastic coupling between positive magnetostriction and internal stress in the specimen.
49 citations
TL;DR: In this paper, a new metallic glass, (METGLAS®alloy) Co 74 Fe 6 B 20, has been identified which exhibits ∼ zero magnetostriction ( |lambda_{s}| ), the saturation induction of this new alloy, 11.8 kG, is approximately twice that reported for other nonmagnetostrictive glasses with similar transition-metal (TM) content but including the metalloids P and Al or Si in addition to B.
Abstract: A new metallic glass, (METGLAS®alloy) Co 74 Fe 6 B 20 , has been identified which exhibits ∼ zero magnetostriction ( |\lambda_{s}| ). The saturation induction of this new alloy, 11.8 kG, is approximately twice that reported for other non-magnetostrictive glasses with similar transition-metal (TM) content but including the metalloids P and Al or Si in addition to B. This larger magnetization results from the weaker hybridization of the TM d-bands with the valence bands of boron than with those of other metalloids. Due to the absence of magnetostriction, no coupling between winding stresses and magnetic properties exists. Hence, as-quenched/as-wound toroids of Co 74 Fe 6 B 20 glass exhibit exceptional low-field magnetic properties: H_{c} = 0.035 Oe, B_{r} = 9800 gauss and \mu_{max} = 280,000 .
45 citations
TL;DR: In this article, the effect of carburation on the hyperfine parameters and the different contributions to the internal magnetic field are thoroughly discussed, and a model of itinerant magnetism can account for the various observed magnetic anomalies: first-order transitions, unresolved magnetic Mossbauer spectra, deviation from unity of the ratio of the magnetic moment deduced from the Curie constant to the magnetic moments at saturation, deviations from the linear moment-field relation.
Abstract: Mossbauer spectra on 57Fe and 119Sn in perovskite carbides with formula M3M'C (where M is Fe or Mn, and M', Al, Ga, Ge, Zn, Sn) have been observed. All those compounds are characterized by a large quadrupole coupling amounting to 1.3 mm s-1 and by low internal magnetic fields, around 70 kOe, at M atom. The effect of carburation on the hyperfine parameters and the different contributions to the internal magnetic field are thoroughly discussed. Only a model of itinerant magnetism can account for the various observed magnetic anomalies: first-order transitions, unresolved magnetic Mossbauer spectra, deviation from unity of the ratio of the magnetic moment deduced from the Curie constant to the magnetic moment at saturation, deviation from the linear moment-field relation.
TL;DR: In this article, the propagation characteristics of magnetoelastic surface waves in a delay line consisting of a ferromagnetic film deposited on a piezoelectric substrate were investigated.
Abstract: This paper treats the propagation characteristics of magnetoelastic surface waves in a delay line consisting of a ferromagnetic film deposited on a piezoelectric substrate Magnetoelastic coupling within the film and mechanical coupling between the film and substrate enables the acoustic velocity to be varied by changing the magnetic bias field A theory to predict the dependence of the surface wave velocity upon applied dc magnetic field, material constants, and frequency is presented The velocity change occurs predominantly in a bias field range where the static magnetization vectors are undergoing a rotation The two orientations of the magnetic field in the sagittal plane considered exhibit significantly different characteristics With the field parallel to the direction of propagation the velocity first decreases, attains a minimum, and then increases toward a saturation value as the external field is increased With the field normal to the plane of the film, the velocity increases monotonically toward a saturation value with an increase in field The calculated velocity changes are in good agreement with changes measured on a Ni‐LiNbO3 delay line
TL;DR: In this article, the low-field magnetic properties of Fe80B20 glass are examined for straight strips, stressed and unstressed, for as-cast/as-wound toroids and for field-annealed toroids.
Abstract: The low‐field magnetic properties of Fe80B20 glass are examined. Measurements are reported for straight strips, stressed and unstressed, for as‐cast/as‐wound toroids and for field‐annealed toroids. Due to the positive magnetostriction (λs=31×10−6) of the alloy, the low‐field magnetic properties of strips are improved by applied tensile stress. Similarly, toroids annealed to remove compressive stresses induced by winding (cooled in a magnetic field) are superior to unannealed toroids. Field‐annealed Fe80B20 toroids show a coercivity of ∼0.04 Oe, a permeability of 4000 at 20 G, and a remanence ratio of 0.77Bs(Bs=16 kG). The approach of the magnetization to saturation for field‐annealed toroids indicates a magnetic anisotropy energy density of about 5×103 erg/cm3. This low magnetic anisotropy, as well as the low coercivity and high resistivity (145 μΩ cm±10%) exhibited by Fe80B20 lead to low core loss under ac excitation, i.e., 0.10 W/kg (measured at 1 kHz and a maximum induction of 1 kG on a field‐annealed ...
TL;DR: In this article, the authors introduced magnetization effects into previous calculations of the Mossbauer lineshape of a paramagnetic powder under applied field (which are actually relevant in the case of diamagnetic ions only).
TL;DR: In this article, the molecular field coefficients for the individual rare earth iron garnets have been determined by a trial and error procedure using the phenomenological molecular field theory of Neel and the experimental curves for each rare-earth iron garnet.
Abstract: The molecular field coefficients for the individual rare earth iron garnets have been determined by a trial and error procedure using the phenomenological molecular field theory of Neel and the experimental curves for each rare-earth iron garnet. These results were then used to calculate magnetic moment-temperature curves for various film compositions subject to the conditions that the lattice parameter of the film and λ
TL;DR: In this article, magnetization measurements are reported for the alloy series, Ni2MnxTi1−xSn, where T is Ti, V, or Cr, and the samples are polyphase.
Abstract: Magnetization measurements are reported for the alloy series, Ni2MnxTi1−xSn, where T is Ti, V, or Cr. Alloys containing Ti or V were studied at compositions corresponding to x = 1, 0.8, 0.6, 0.4, 0.2, and 0.0. The Cr series was studied for x = 1, 0.8, 0.6, and 0.4; beyond this composition, the samples are polyphase. For the Ti series, all of the alloys containing Mn are ferromagnetic with Currie temperatures in the range 345 K to 261 K, and saturation moments in the range 4.04 μB to 0.47 μB per molecule. All of the V alloys containing Mn are ferromagnetic with Curie points between 345 K and 45 K, and saturation moments between 4.04 μB and 0.60 μB per molecule. Curie points for the Cr series range between 345 K and 220 K and the saturation moments vary from 4.04 μB to 2.11 μB per molecule. Susceptibility studies on the Ti, V, and Cr series show Curie–Weiss behaviour and indicate an effective moment of ~5 μB per Mn atom. The interpretation of the results is consistent with a contribution of ~ −1 μB by a Ti ...
Patent•
01 Mar 1976
TL;DR: In this paper, a series of glassy metal alloys with near zero magnetostriction was disclosed, and they have the composition (Cox Fe1 -x)a Bb Cc, where x ranges from about 0.84 to 1.0, a ranges from 78 to 85 atom percent, b ranges from 10 to 22 atom percent and c ranges from 0 to 12 atom percent.
Abstract: A new series of glassy metal alloys with near-zero magnetostriction is disclosed. The glassy alloys have the composition (Cox Fe1 -x)a Bb Cc, where x ranges from about 0.84 to 1.0, a ranges from about 78 to 85 atom percent, b ranges from about 10 to 22 atom percent and c ranges from 0 to 12 atom percent, with the proviso that the sum of b and c ranges from about 15 to 22 atom percent. The magnetostriction of these alloys ranges from about +5 × 10- 6 to -5 × 10- 6 and the saturation induction is at least about 10 kGauss. The transition metal content is responsible for the low magnetostriction in these alloys, as well as their high saturation induction. The metalloid content (needed to stabilize the glassy state which is one of low anisotropy) strongly affects the saturation induction and Curie temperature, but not the magnetostriction.
TL;DR: In this article, the saturation of a magnetic recording head has been studied by numerically solving for the scalar magnetic potential in a region which includes the pole tip corners, and it is shown that saturation of the pole corner primarily affects the recording field gradients and does so appreciably only when the deep-gap field exceeds one half the material saturation magnetization.
Abstract: The saturation of a magnetic recording head has been studied by numerically solving for the scalar magnetic potential in a region which includes the pole tip corners. The method follows Monson in which the bulk saturation behavior provides the boundary conditions. It is shown that saturation of the pole corner primarily affects the recording field gradients and does so appreciably only when the deep-gap field exceeds one half the material saturation magnetization. The field magnitudes are only slightly affected and remain dominated by the bulk saturation. It is argued that reductions in short-wavelength recorded signal should occur when the recording medium coercivity exceeds approximately one-quarter the saturation magnetization of the head material. This condition is almost reached by the utilization of ferrite record heads ( M_{s} \cong 4-5 kG) to record on high coercivity media ( H_{c} \cong 1000 Oe). The computation is restricted to two dimensions and the effects of losses, such as eddy currents, have not been included.
TL;DR: The Mossbauer effect has been used to investigate the magnetic properties of Cu-Fe alloys of concentration 0.24-4.6% in the temperature range 4.2-100K and in applied magnetic fields of up to 8.0 T.
Abstract: The Mossbauer effect has been used to investigate the magnetic properties of Cu-Fe alloys of concentration 0.24-4.6% Fe in the temperature range 4.2-100K and in applied magnetic fields of up to 8.0 T. Alloys containing more than about 0.5% Fe exhibited magnetic broadening at 4.2K and the transition temperatures at which the broadening first occurred have been determined. The distributions of hyperfine magnetic fields observed in these specimens below the transition temperatures have been studied as functions of iron concentration and of temperature. The saturation hyperfine fields for isolated iron atoms are found to vary with concentration, exhibiting a linear variation at high concentrations but falling more rapidly at lower concentration. This is interpreted as evidence for the formation of a Kondo state. Spectra obtained at high magnetic fields indicate some anisotropy in the impurity response to the applied field.
01 Sep 1976
TL;DR: In this paper, the structural disorder has influence on the magnetic excitations rather than the magnetic moment, and the contribution of structural disorder to the magnetic properties is found directly by comparing the results for the amorphous Fe80P13C7 and Co75Si15B10 with those for the corresponding single phase crystalline bcc Fe•P‐C and hcp Co•Si•B, which were obtained by careful thermal treatments.
Abstract: Detailed magnetic measurements were carried out on amorphous alloys: Fe‐Co‐P‐C, Fe‐Cr‐P‐C and Co‐Fe‐SI‐B. The saturation magnetizations (Ms) are obtained for these alloys using the formula dM/dH = Ms(a/H2) + Xo. The spin‐wave dispersion coefficients (D) are also obtained from the low temperature magnetization measurements. The contribution of the structural disorder to the magnetic properties is found directly by comparing the results for the amorphous Fe80P13C7 and Co75Si15B10 with those for the corresponding single‐phase crystalline bcc Fe‐P‐C and hcp Co‐Si‐B, which were obtained by careful thermal treatments. The results show that the structural disorder has influence on the magnetic excitations rather than the magnetic moment.
TL;DR: Amorphous Gd x Fe 1-x (0 < x < 0.35) thin films were prepared by RF cosputtering using an iron target covered partially with small gadolinium pieces as mentioned in this paper.
Abstract: Amorphous Gd x Fe 1-x (0 < x < 0.35) thin films were prepared by RF cosputtering using an iron target covered partially with small gadolinium pieces. The composition dependences of saturation magnetization, hysteresis curves, and domain structures were studied. Spark-like domains were observed when the magnetization was reversed from saturation. The uniaxial anisotropy was induced perpendicular to the film plane. The average value of the perpendicular uniaxial anisotropy constant Ku was about 2 × 105erg/cm3. Ku, however, decreases as the saturation moment decreases in the vicinity of room temperature compensation. The stripe domain width was varied from 0.3 to 4 microns as the saturation moment decreased from 300 to 20 gauss. These magnetic properties of amorphous Gd-Fe sputtered films are similar to those of amorphous Gd-Co films.
TL;DR: In this paper, the importance of a thermal perturbation of (0.1%) under excitation by long (up to 30 msec) electron beam pulses is investigated using the measured differential thermal behavior of luminescence lines originating in the,, and states.
Abstract: The importance of a thermal perturbation of (0.1%) under excitation by long (up to 30 msec) electron beam pulses is investigated using the measured differential thermal behavior of luminescence lines originating in the , , and states. An observed droop in light output, equivalent to a saturation of the phosphor brightness, is found to be inconsistent with a thermal perturbation of the system. Other experiments involving a‐c electric field modulation of the luminescence from the states suggest that the droop may be caused by electric field perturbation of the system. The saturation characteristics of the phosphor are changed reversibly during a 30 msec pulse, and irreversibly by mixing with a conducting matrix. It is suggested that space‐charge fields are generated by trapping of charge in surface states of the phosphor grains, and a simple kinetic model for the saturation mechanism involving field‐induced ionization of the charge transfer state and quenching of the state is in qualitative agreement with the experimental data. The relevance of the model to saturation phenomena and to aging in CRT screens is discussed.
TL;DR: In this paper, the relative microwave power saturation behavior of allowed main transitions and forbidden satellite transitions has been examined in two systems: 63Cu-doped CaCd (OAc)4·6H2O single crystals and PO32− in γ-irradiated Na2HPO3·5H2Os single crystals.
TL;DR: In this paper, a numerical approach to the determination of the magnetic field distribution, in a semi-infinite space, filled with conductive ferromagnetic materiaI, is presented.
Abstract: This paper offers a numerical approach to the determination of the magnetic field distribution, in a semi-infinite space, filled with conductive ferromagnetic materiaI. Simple mathematical functions are used to simulate the saturation and hysteresis characteristics of a given material. The case of a sinusoidal magnetic field, applied uniformly on the boundary plane, is studied as an example. The paper offers an analysis of the field distribution during the transient period, as well as an evaluation of steady-state characteristics like surface current density, penetration depth, power los - ses and power factor. The comparison of steady-state results with those given by other methods, is discussed at the end of the paper.
TL;DR: In this paper, the microwave power saturation behavior of an inhomogeneously broadened electron paramagnetic resonance line with detection at the second harmonic of the magnetic field modulation frequency under slow-passage conditions has been derived.
TL;DR: In this paper, the dependence of the photoelectron spin polarization on photon energy has been measured on surfaces of single crystals obtained by cleaving in ultrahigh vacuum, and the results are quantitatively explained by the model of a single ion in a crystal field (SICF) with only few adjustable parameters.
TL;DR: In this paper, two record heads of identical construction but different core materials, mumetal and a high-saturation-magnetization iron-cobalt alloy, were used for recording 165 flux changes per cm (420 fci).
Abstract: Digital recording is usually achieved by driving the record-head core material to only 30-40% of its saturation magnetization. Saturation of the core material will occur only when attempting to record on magnetic media of very high coercive force. Magnetic recording materials with coercive forces of 1100, 1800, and 3600 oersteds have been investigated for low-density digital recording on magnetic-stripe cards. Two record heads of identical construction but different core materials, mumetal and a high-saturation-magnetization iron-cobalt alloy, were used for recording 165 flux changes per cm (420 fci). The initiation of pole-tip saturation in both heads was detected by the decrease in inductance. The mumetal head was unable to fully record either the 1800 or 3600-Oe coercive-force materials because of pole-tip saturation. The high-field head recorded all materials.
TL;DR: The saturation magnetostriction of gadolinium single crystal has been measured from 4.2 K to 330 K, above the Curie temperature, by a strain gauge technique as discussed by the authors.
Abstract: The saturation magnetostriction of gadolinium single crystal has been measured from 4.2 K to 330 K, above the Curie temperature, by a strain gauge technique. The anomalous saturation magnetostrictions along the c - and a -axes in the a c plane were observed at low temperatures. These anomalies are explained by the higher order terms of the magnetostriction constants.