Showing papers on "Curie temperature published in 2012"
TL;DR: The Skyrmion state in epitaxial B20 FeGe(111) thin films, determined by the topological Hall effect, is greatly extended in the phase diagram to cover all temperatures up to the Curie temperature T(C)≈271 K and over a wide magnetic field range that includes a zero magnetic field.
Abstract: The Skyrmion state in epitaxial B20 FeGe(111) thin films, determined by the topological Hall effect, is greatly extended in the phase diagram to cover all temperatures up to the Curie temperature ${T}_{C}\ensuremath{\approx}271\text{ }\text{ }\mathrm{K}$ and over a wide magnetic field range that includes a zero magnetic field. The properties of the Skyrmion phase can be controlled and manipulated by the film thickness, which has a strong effect on the stabilization of Skyrmions.
444 citations
TL;DR: In this paper, a quasi-quadruple point system with four phases (Cubic-Tetragonal-Orthorhombic-Rhombohedral) nearly coexist together in the temperature-composition phase diagram was studied.
Abstract: We report ultrahigh dielectric and piezoelectric properties in BaTiO3-xBaSnO3 ceramics at its quasi-quadruple point, a point where four phases (Cubic-Tetragonal-Orthorhombic- Rhombohedral) nearly coexist together in the temperature-composition phase diagram. At this point, dielectric permittivity reaches ∼ 75000, a 6-7-fold increase compared with that of pure BaTiO3 at its Curie point; the piezoelectric coefficient d33 reaches 697 pC/N, 5 times higher than that of pure BaTiO3. Also, a quasi-quadruple point system exhibits double morphotropic phase boundaries, which can be used to reduce the temperature and composition sensitivity of its high piezoelectric properties. A Landau-Devonshire model shows that four-phase coexisting leading to minimizing energy barriers for both polarization rotation and extension might be the origin of giant dielectric and piezoelectric properties around this point. Copyright c � EPLA, 2012
211 citations
TL;DR: In this article, a diamagnetic layered dichalcogenide solid, Molybdenum disulphide, was found to show magnetic ordering at room temperature when exposed to a 2 MeV proton beam.
Abstract: Molybdenum disulphide, a diamagnetic layered dichalcogenide solid, is found to show magnetic ordering at room temperature when exposed to a 2 MeV proton beam. The temperature dependence of magnetization displays ferrimagnetic behavior with a Curie temperature of 895 K. A disorder mode corresponding to a zone-edge phonon and a Mo valence higher than +4 has been detected in the irradiated samples using Raman and x-ray photoelectron spectroscopy, respectively. The possible origins of long-range magnetic ordering in irradiated MoS2 samples are discussed.
196 citations
TL;DR: In this paper, a systematic study of the magnetic properties and both the temperature and magnetic-field-induced structural transformations in the Ni 50− x Co x Mn 39 Sn 11 (0 ⩽ x ⌽ 10 ) multifunctional alloys over a large temperature range from 500 k down to 10 k was performed.
179 citations
TL;DR: In this paper, a diamagnetic layered dichalcogenide solid, Molybdenum disulphide, was found to show magnetic ordering at room temperature when exposed to a 2 MeV proton beam.
Abstract: Molybdenum disulphide, a diamagnetic layered dichalcogenide solid, is found to show magnetic ordering at room temperature when exposed to a 2 MeV proton beam. The temperature dependence of magnetization displays ferrimagnetic behavior with a Curie temperature of 895 K. A disorder mode corresponding to a zone-edge phonon and a Mo valence higher than +4, have been detected in the irradiated samples using Raman and X-ray photoelectron spectroscopy, respectively. The possible origins of long-range magnetic ordering in irradiated MoS2 samples are discussed.
164 citations
TL;DR: In this paper, a series of manganese-doped hierarchical microspheres (HMSs) are prepared by hydrothermal method only using zinc acetate precursors and ethylene glycol as solvent, and X-ray diffraction indicates that all of the as-obtained samples including the highest Mn (7 mol%) in the crystal lattice of ZnO have a pure phase.
Abstract: In this study, a series of manganese [Mn]-doped zinc oxide [ZnO] hierarchical microspheres [HMSs] are prepared by hydrothermal method only using zinc acetate and manganese acetate as precursors and ethylene glycol as solvent. X-ray diffraction indicates that all of the as-obtained samples including the highest Mn (7 mol%) in the crystal lattice of ZnO have a pure phase (hexagonal wurtzite structure). A broad Raman spectrum from as-synthesized doping samples ranges from 500 to 600 cm-1, revealing the successful doping of paramagnetic Mn2+ ions in the host ZnO. Optical absorption analysis of the samples exhibits a blueshift in the absorption band edge with increasing dopant concentration, and corresponding photoluminescence spectra show that Mn doping suppresses both near-band edge UV emission and defect-related blue emission. In particular, magnetic measurements confirm robust room-temperature ferromagnetic behavior with a high Curie temperature exceeding 400 K, signifying that the as-formed Mn-doped ZnO HMSs will have immense potential in spintronic devices and spin-based electronic technologies.
161 citations
TL;DR: In this paper, an energy efficient method for the synthesis of superparamagnetic ferrite (Fe 3 O 4 ) nanoparticles (10-40nm) and their annealing effect on the morphology, size, curie temperature and magnetic behavior at 50, 300, 400 and 500 Â c.
159 citations
TL;DR: In this article, a new form of magnetism has been discovered: the coexistence of strong and weak magnetism in alternate atomic layers, which can be used for refrigeration and energy conversion.
Abstract: The efficient coupling between lattice degrees of freedom and spin degrees of freedom in magnetic materials can be used for refrigeration and energy conversion. This coupling is enhanced in materials exhibiting the giant magnetocaloric effect. First principle electronic structure calculations on hexagonal MnFe(P, Si) reveal a new form of magnetism: the coexistence of strong and weak magnetism in alternate atomic layers. The weak magnetism of Fe layers (disappearance of local magnetic moments at the Curie temperature) is responsible for a strong coupling with the crystal lattice while the strong magnetism in adjacent Mn-layers ensures Curie temperatures high enough to enable operation at and above room temperature. Varying the composition on these magnetic sublattices gives a handle to tune the working temperature and to achieve a strong reduction of the undesired thermal hysteresis. In this way we design novel materials based on abundantly available elements with properties matched to the requirements of an efficient refrigeration or energy-conversion cycle.
151 citations
TL;DR: In this article, the Curie temperature and the existence of an impurity band for the holes in a ferromagnetic semiconductor has been investigated and a direct link between TC and the presence of impurity bands for holes has been established.
Abstract: Although (Ga,Mn)As is considered the model ferromagnetic semiconductor, the electronic structure of the charges — holes in this case — and its connection with the Curie temperature (TC) are still unclear. Experiments now provide a direct link between TC and the existence of an impurity band for the holes. Clarifying this issue is essential to designing other materials with potentially higher TC.
146 citations
TL;DR: In this article, temperature-induced anomalies in the dielectric, piezoelectric and elastic coefficients and Raman spectroscopy of ceramic BCZT were reported.
Abstract: The solid solution 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising lead-free piezoelectric material with exceptionally high piezoelectric coefficients. The strong response is related to structural instabilities close to ambient temperature. We report here on temperature-induced anomalies in the dielectric, piezoelectric, and elastic coefficients and Raman spectroscopy of ceramic BCZT. The data indicate ferroelectric-ferroelectric structural phase transitions in this material in addition to those previously reported. An anomaly is also observed above the Curie temperature TC and is associated with the loss of polar structure that persists thirty degrees above TC.
145 citations
TL;DR: In this paper, the structural, magnetic, and magnetoelectrical properties of Bi2Se3 were investigated for Cr concentrations up to 10% for a Cr content up to ∼5% the films are of good crystalline quality, with the lattice parameter decreasing with increasing Cr concentration.
Abstract: We report on the observation of ferromagnetism in epitaxial thin films of the topological insulator compound Bi2Se3 with chromium doping. The structural, magnetic, and magnetoelectrical properties of Bi2Se3 were investigated for Cr concentrations up to 10%. For a Cr content up to ∼5% the films are of good crystalline quality, with the lattice parameter a decreasing and the lattice parameter c increasing with increasing Cr concentration. The Curie temperature reached a maximum TC = 20 K for 5.2% Cr. Well-defined ferromagnetic hysteresis in the magnetization and in the magnetoresistance was also observed in these films.
TL;DR: In this paper, an electric double layer (EDL) formed in a polymer film containing an ionic liquid was applied to a Co ultra-thin film and the change in the Curie temperature was investigated.
Abstract: The electric field effect on magnetization properties and Curie temperature of Co ultra-thin films has been investigated. An electric field is applied to a Co film by using an electric double layer (EDL) formed in a polymer film containing an ionic liquid. The change in the Curie temperature is ∼100 K by applying the gate voltage of ±2 V, suggesting that the observed large modifications of magnetization properties are attributed to the significant change in the Curie temperature, which is induced by a large amount of carrier density control due to the formation of the EDL.
TL;DR: In this article, BaZrO3-(1−x)BaTiO3 solid solutions (x = 0, 004, 006, 008, 012, and 018) were synthesized via conventional solid state reaction method.
Abstract: xBaZrO3-(1−x)BaTiO3 solid solutions (x = 0, 004, 006, 008, 012, and 018) synthesized via conventional solid state reaction method exhibit piezoelectric coefficients comparable to those of “hard” PZT-8, PZT-4, and even “soft” PZT-5 A Doping also improves the poling efficiency of xBaZrO3-(1−x)BaTiO3 ceramics Study of temperature dependence of the dielectric and piezoelectric properties reveal the following Doping lowered the Curie point but raised the temperatures of the other two transformations The diffused phase transition behavior has been enhanced with increasing content of BaZrO3, but x ≤ 018 is not enough to show a relaxor behavior Piezoelectric responses show peaks at transformation temperatures and exhibit the best stability in the orthorhombic phase Significant improvement in room temperature piezoelectric and electromechanical responses (d33 = 420pC/N, d31 = −138pC/N, and kp = 49%) comparable to PZT-5 A is achieved at a composition of x = 006 (1400 °C 100 h sintered), which brings the rhombohedral-orthorhombic transition to the ambient temperature Enhanced piezoelectric properties are mainly attributed to a series of microscopic phase transformations due to the presence of internal structural gradient Other possible contributions such as domain structures and constrained negative stiffness effect have also been discussed
TL;DR: In this paper, the particle size effect on the magnetic properties and phase transitions in BiFeO 3 samples prepared by spray pyrolysis method has been studied and the phase purity and structure have been investigated by XRD and FTIR spectroscopy analysis.
TL;DR: In this article, the authors combine results of channeling experiments, which measure the concentrations both of Mn ions and of holes relevant to the ferromagnetic order, with magnetization, transport, and magneto-optical data to address this issue.
Abstract: The ferromagnetic semiconductor (Ga,Mn)As has emerged as the most studied material for prototype applications in semiconductor spintronics. Because ferromagnetism in (Ga,Mn)As is hole-mediated, the nature of the hole states has direct and crucial bearing on its Curie temperature TC. It is vigorously debated, however, whether holes in (Ga,Mn)As reside in the valence band or in an impurity band. In this paper we combine results of channeling experiments, which measure the concentrations both of Mn ions and of holes relevant to the ferromagnetic order, with magnetization, transport, and magneto-optical data to address this issue. Taken together, these measurements provide strong evidence that it is the location of the Fermi level within the impurity band that determines TC through determining the degree of hole localization. This finding differs drastically from the often accepted view that TC is controlled by valence band holes, thus opening new avenues for achieving higher values of TC.
TL;DR: In this article, a morphotropic phase boundary (MPB) composition for polycrystalline ceramics using columbite precursor method was synthesized and the optimum properties were found for the MPB composition 0.33 and 0.36, confirmed by their respective dielectric and piezoelectric properties.
Abstract: yPb(In1/2Nb1/2)O3–(1 − x − y)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (yPIN–(1 − x − y)PMN–xPT) polycrystalline ceramics with morphotropic phase boundary (MPB) compositions were synthesized using columbite precursor method. X-ray diffraction results indicated that the MPB of PIN–PMN–PT was located around PT = 0.33–0.36, confirmed by their respective dielectric, piezoelectric and electromechanical properties. The optimum properties were found for the MPB composition 0.36PIN–0.30PMN–0.34PT, with dielectric permittivity ɛr of 2970, piezoelectric coefficient d33 of 450 pC/N, planar electromechanical coupling kp of 49%, remanent polarization Pr of 31.6 μC/cm2 and TC of 245 °C. According to the results of dielectric and pyroelectric measurements, the Curie temperature TC and rhombohedral to tetragonal phase transition temperature TR–T were obtained, and the “flat” MPB for PIN–PMN–PT was achieved, indicating that the strongly curved MPB in PMN–PT system was improved by adding PIN component, offering the possibility to grow single crystals with high electromechanical properties and expanded temperature usage range (limited by TR–T).
TL;DR: The canted antiferromagnetic insulating phase in ultra thin films of n<10 coincides with the occurrence of a higher symmetry structural phase with a different oxygen octahedra rotation pattern, which is an interesting candidate for an insulating tunneling barrier in room temperature spin polarized tunneling devices.
Abstract: We present a study of the thickness dependence of magnetism and electrical conductivity in ultrathin La0.67Sr0.33MnO3 films grown on SrTiO3 (110) substrates. We found a critical thickness of 10 unit cells below which the conductivity of the films disappeared and simultaneously the Curie temperature increased, indicating a magnetic insulating phase at room temperature. These samples have a Curie temperature of about 560 K with a significant saturation magnetization of 1.2±0.2μB/Mn. The canted antiferromagnetic insulating phase in ultra thin films of n<10 coincides with the occurrence of a higher symmetry structural phase with a different oxygen octahedra rotation pattern. Such a strain engineered phase is an interesting candidate for an insulating tunneling barrier in room temperature spin polarized tunneling devices.
TL;DR: The spin polarization of ferromagnetic Heusler alloys, Co 2 Fe(Ga x Ge 1−x ) ( x ǫ = 0, 0.75, and 1), is investigated by point contact Andreev reflection (PCAR) measurements as discussed by the authors.
TL;DR: In particular, BFMT-BT ceramics with a pseudocubic perovskite crystal structure exhibit remarkably high-temperature stable piezoelectric properties as mentioned in this paper.
Abstract: Dense (1-y)BiFe1−x(Mg0.5Ti0.5)xO3 − yBaTiO3 (BFMT-BT, y = 0.29, x = 0-0.12) ceramics with a pseudocubic perovskite crystal structure exhibit remarkably high-temperature stable piezoelectric properties. In particular, x = 0.03 BFMT-BT ceramics, with a Curie temperature, Tc, of ∼425 °C, show a stable piezoelectric coefficient, d33, of ∼155 pC/N up to a depolarization temperature, Td, of ∼400 °C. This Td is higher than Tc for Pb(Zr,Ti)O3, therefore suggesting BFMT-BT ceramics to be promising high-temperature Pb-free piezoelectric materials.
TL;DR: It is reported that a YbFO thin-film heterostructure fabricated by adopting a hexagonal template surprisingly exhibits nonferroelastic ferroelectricity with the Curie temperature of 470 K.
Abstract: Multiferroics have received a great deal of attention because of their fascinating physics of order-parameter cross-couplings and their potential for enabling new device paradigms. Considering the rareness of multiferroic materials, we have been exploring the possibility of artificially imposing ferroelectricity by structurally tailoring antiferromagnets in thin-film forms. YbFeO3 (YbFO hereafter), a family of centrosymmetric rare-earth orthoferrites, is known to be nonferroelectric (space group Pnma). Here we report that a YbFO thin-film heterostructure fabricated by adopting a hexagonal template surprisingly exhibits nonferroelastic ferroelectricity with the Curie temperature of 470 K. The observed ferroelectricity is further characterized by an extraordinary two-step polarization decay, accompanied by a pronounced magnetocapacitance effect near the lower decay temperature, ∼225 K. According to first-principles calculations, the hexagonal P63/mmc–P63mc–P63cm consecutive transitions are primarily respons...
TL;DR: Dy3+ substituted Ni-Cu-Zn (Ni0.4Cu 0.4Zn 0.2DyxFe2−xO4) ferrite nanoparticles were obtained at 600°C by synthesizing sol-gel auto-combustion method, and they exhibit a particle size of 12-21'nm.
Abstract: Dy3+ substituted Ni-Cu-Zn (Ni0.4Cu0.4Zn0.2DyxFe2−xO4) ferrite nanoparticles were obtained at 600 °C by synthesizing sol-gel auto-combustion method, and they exhibit a particle size of 12–21 nm. X‐ray diffraction patterns confirm the presence of secondary phase of DyFeO3 and Fe2O3 for the Dy3+ substituted samples. Ni‐Cu‐Zn ferries doped with Dy3+ possess better grain structure and growth than that of pure Ni‐Cu‐Zn ferrite. The saturation magnetization increases remarkably up to 81 emu/g with increasing the Dy3+ ions. The increased saturation magnetization related to increased exchange interactions between Fe‐Fe ions and also with increased particle size. Blocking temperature was found to decrease with increasing Dy3+ substitution. An enhancement in initial permeability and Curie temperature was observed with Dy3+ substitution.
TL;DR: In this paper, a temperature dependent negative capacitance (NC) effect in a metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structure was shown to be correlated with the S-shape of the polarization versus electrical field characteristics.
Abstract: In this paper, we report the basic design conditions and the experimental confirmation of a temperature dependent negative capacitance (NC) effect in a ferroelectric field-effect-transistor (Fe-FET). We find that the internal voltage amplification peaks of a metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structure are correlated with the S-shape of the polarization versus electrical field characteristics. The internal voltage amplification is responsible for the subthreshold swing reduction in a Fe-FET; this effect cancels out when the temperature is increased close to the Curie temperature because of the narrowing of the NC region and because of the saturation of the amplification. A counter-clockwise rotation of the P-V loops with an associated increase of the dP/dV slope with the temperature is reported, which corresponds to an increase of the overall ferroelectric capacitance with the temperature. Finally, we theoretically and experimentally demonstrate that an optimum temperature exists at which the amplification gets its maximum. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704179]
TL;DR: In this paper, the structural and magnetic properties of Co1−xZnxFe2O4 nanoparticles synthesized by the chemical co-precipitation method were investigated.
TL;DR: In this paper, a new piezoelectric ceramics, 0.71BiFe1−x(Ni1/2Ti 1/2)x O3−0.29BaTiO3+0.09, were fabricated using conventional mixed-oxide method.
Abstract: New piezoelectric ceramics, 0.71BiFe1−x(Ni1/2Ti1/2)x O3−0.29BaTiO3+0.6 wt% MnO2 [BFNTx–BT] (x = 0–0.09), were fabricated using conventional mixed-oxide method. It was found that the introduction of BNT into BF-BT system caused insignificant change in crystal structure, which is a single-phase perovskite structure. However, an obvious variation in microstructure took place. The ceramics with composition of x = 0.03 showed enhanced piezoelectric, electromechanical, and ferroelectric properties with piezoelectric constant d33 = 156 pC/N, planar electromechanical coupling factors kp = 0.308, remnant polarization Pr = 22.5 μC/cm2, and coercive field Ec = 28.2 kV/cm, with a high Curie temperature Tc = 431°C, respectively. The combination of good piezoelectric properties and high Tc makes these ceramics suitable for elevated temperature piezoelectric devices.
TL;DR: In this article, phase transitions and magnetic properties of melt spun Mn55Al45 based alloys doped with C, B, and rare earth (RE) elements were investigated, and the phase transformations between the e and the L10 (τ) phase are of interest.
Abstract: MnAl alloys are attractive candidates to potentially replace rare earth hard magnets because of their superior mechanical strength, reasonable magnetic properties, and low cost. In this study, the phase transitions and magnetic properties of melt spun Mn55Al45 based alloys doped with C, B, and rare earth (RE) elements were investigated. As-spun Mn–Al, Mn–Al–C, and Mn–Al–C–RE ribbons possessed a hexagonal e crystal structure. Phase transformations between the e and the L10 (τ) phase are of interest. The e → τ transformation occurred at ~500 °C and the reversed τ → e transformation was observed at ~800 °C. Moderate carbon addition promoted the formation of the desired hard magnetic L10 τ-phase and improved the hard magnetic properties. The Curie temperature T
C of the τ phase is very sensitive to the C concentration. Dy or Pr doping in MnAlC alloy had no significant effect on T
C. Pr addition can slightly improve the magnetic properties of MnAlC alloy, especially JS. Doping B could not enhance the magnetic properties of MnAl alloy since B is not able to stabilize either the e phase or the L10 hard magnetic τ phase.
TL;DR: In this paper, a Bragg-Williams approximation was proposed to describe the observed behavior in terms of the evolution of the magnetic contribution to the total entropy change in metamagnetic shape memory alloys.
TL;DR: In this article, the effect of grain size distribution on the Curie temperature (Tc) dispersion with relevance to heat assisted magnetic recording is investigated. But the authors focus on the magnetic phase transition behavior in an L10 FePt system.
Abstract: We present atomistic calculations of the magnetic phase transition behavior in an L10 FePt system to study the effect of grain size distribution on the Curie temperature (Tc) dispersion with relevance to heat assisted magnetic recording. Identifying the relation between the size and Tc of a grain by means of finite size scaling analysis of the differentiated magnetization versus T data allows to show that a lognormal size distribution transforms into a lognormal Tc distribution with moments dependent on the critical exponents. We also address the question of the universality class of FePt.
TL;DR: In this paper, a different kind of multiferroics with ferroelectric-ferrimagnetic (FE-FM) composites: PbZr0.53Ti0.47O3 and Ni0.65Zn0.35Fe2O4 with x = 0.10, 0.20 and 0.30, were synthesized by a powder-in-sol precursor hybrid processing route.
Abstract: A different kind of multiferroics with ferroelectric–ferrimagnetic (FE–FM) composites: (1 − x) PbZr0.53Ti0.47O3–x Ni0.65Zn0.35Fe2O4 with x = 0.10, 0.20 and 0.30, were synthesized by a powder-in-sol precursor hybrid processing route. Structural analysis with X-ray diffraction (XRD) data revealed the presence of both PbZr0.53Ti0.47O3 (PZT) and Ni0.65Zn0.35Fe2O4 (NZFO) pure phases in the PZT–NZFO composites. Scanning electron micrographs (SEM) clearly disclose distribution of both PZT and NZFO phases throughout the sample. Dielectric and electrical properties of the system have been investigated in a wide range of frequency at different temperatures. Dielectric constant (er) as a function of temperature reveals the paraelectric–FE transition temperature at ~408 °C having maximum value of er at the peak [e
r
max
= 1,200] with another low temperature anomaly at ~297 °C, very close to the magnetic Curie temperature of the NZFO ferrite (Tc = 300 °C) for the x = 0.1 FE–FM composite. The impedance spectroscopy data of these composites show clearly, contribution of both grain and grain boundary effect in the electrical properties of the composites. Negative temperature coefficient of resistance (NTCR) behavior of the materials indicates their semi-conducting nature. The ac conductivity spectrum is found to obey Johnscher’s power law very well. The temperature-dependent magnetization hysteresis (M–H) loops of the PZT/NZFO composite show excellent non-saturating ferrimagnetic behavior with increase in both coercive field (Hc) and remanent magnetization (Mr) when the NZFO content in the composite is increased. Polarization (P) versus electric field (E) studies at 300 K give conclusive evidence of the presence of spontaneous polarization in all the three composites (x = 0.1, 0.2 and 0.3). However, area of P–E loop, coercive field (Ec) and remanent polarization (Pr) are found to decrease noticeably with the increase of the NZFO content (x) in these composites.
TL;DR: It is found that polarization and the piezoelectric coefficient increase by about 20% and 250%, respectively, in this strain range and these trends are well reproduced by first-principles-based techniques.
Abstract: Epitaxial strain has recently emerged as a powerful means to engineer the properties of ferroelectric thin films, for instance to enhance the ferroelectric Curie temperature (T(C)) in BaTiO(3). However, in multiferroic BiFeO(3) thin films an unanticipated strain-driven decrease of T(C) was reported and ascribed to the peculiar competition between polar and antiferrodistortive instabilities. Here, we report a systematic characterization of the room-temperature ferroelectric and piezoelectric properties for strain levels ranging between -2.5% and +1%. We find that polarization and the piezoelectric coefficient increase by about 20% and 250%, respectively, in this strain range. These trends are well reproduced by first-principles-based techniques.
TL;DR: In this paper, the effect of holmium substitution on the magnetic properties of CoHo x Fe 2− x O 4 ferrites was investigated using co-precipitation technique.