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The magnetic and magnetocaloric properties of La-deficient manganate single crystals of (La1−x)0.8Ca0.2MnO3 with x=0.05 and 0.20 compositions were investigated. The single crystal with the x=0.05 composition is magnetically more frustrated than that with the x=0.20 composition. The spin-glass transition temperature, Tg, of about 100 K was observed for x=0.05 only. But at x=0.20, a drastic increase in magnetization and Curie temperature was found, as compared to the x=0.05 composition. As a result, for x=0.20, a large magnetic entropy change ΔSM, of about −5.46 J/kg/K for the maximum ΔSM at H=5 T, is associated with the ferromagnetic–paramagnetic transition, which is very applicable for magnetic refrigeration. [Copyright &y& Elsevier]

The neutron irradiation effects of soft magnetic properties in the as-quenched and the annealed amorphous Fe73.5Cu1Nb3Si13.5B9 alloys were studied by complex permeability spectra measurement. The annealing at 823 K caused the decrease of permeability from irreversible domain wall motion but increase the permeability from reversible magnetization, compared to the as-quenched sample. The neutron irradiation in the as-quenched sample increases the permeability from both irreversible and reversible magnetization processes. The neutron irradiation in the annealed sample showed the increase of permeability from irreversible domain wall motion, but decrease of permeability from reversible magnetization. [Copyright &y& Elsevier]

We have investigated the magnetization behavior as a function of field and temperature for amorphous Fe90−xMnxZr10 alloys prepared by a single-roll melt-spinning technique. The temperature dependence of magnetization for these alloys shows the existence of antiferromagnetic couplings between Fe atoms in low fields. The magnetic parameters, obtained from the low temperature magnetization data, are consistent with the presence of mixed magnetic state. With an increase of the concentration of Mn, the Curie temperature decreases almost linearly and then the reentrant behavior is observed in all the samples. The percentage deviation of the fit from the data closely reveals that the combination of both spin wave and single-particle excitations describes the thermal demagnetization process quite well in these ferromagnetic alloys. [Copyright &y& Elsevier]

Soft magnetic properties of melt-spuned (Fe–Co)–Zr alloy system can be achieved upon suitable partial nanocrystallization by proper thermal treatment. In this study, we have measured the spin-wave stiffness constant, magnetoimpedance and incremental permeability ratio (PR) of Fe75−xCoxZr8Nb2B15 (x=5, 10, 15) alloys to investigate the influence of the structural changes in the nanocrystallization process as well as the changes of the magnetic properties as a function of annealing temperatures. With increasing Co content, the spin wave stiffness constant and Curie temperature increase. The full-width at half-maximum in the longitudinal PR curves do not change very much for the samples annealed at various temperatures regardless of the presence of magnetic field during the heat treatment. The broadening MI ratio curves along with increment of frequency may arise from the circumferential permeability, which is somewhat different from the longitudinal permeability. [Copyright &y& Elsevier]

Abstract: The correlation between structure, Curie temperature (T C), line width of EPR spectra and electrical conductivity of Pr1− x Pb x MnO3 (, 0.2, 0.3, 0.4, and 0.5) perovskites is discussed. It was shown that both adiabatic small polaron and variable range hopping models are good for description of conductivity in paramagnetic region but the first one is more suitable for interpretation of temperature dependence of EPR line width in temperature range 1.2 T C

Abstract: The magnetization behaviors have been measured for amorphous () alloys. The Curie temperature is decreased from 243 to 218K with increasing Mn concentration (–6). The magnetization measurements were conducted at temperatures above the Curie temperature in the paramagnetic region. In all samples, the magnetic properties showed superparamagnetic behavior above where the mean magnetic moment of the superparamagnetic spin clusters decreased with increasing temperature. A large magnetic entropy change , which is calculated from vs. curves associated with the ferromagnetic–paramagnetic transitions in amorphous state, has been observed. The maximum of was found to appear in the vicinity of the Curie temperature of the amorphous phase. The value is 2.96, 2.51 and 2.29J/kgK at and 6, respectively. [Copyright &y& Elsevier]

Abstract: Structural characterization and electron spin resonance study of amorphous Fe82Mn4B4Zr10 ribbon with Curie temperature of 262K is presented. According to X-ray diffraction analysis and transmission electron microscopy the alloy represents matrix with embedded micrograin heterogeneities, both existing in amorphous state. Size of the heterogeneities is about 50nm, they show superparamagnetic state up to ∼500K. [Copyright &y& Elsevier]

Highlights • The relation between critical and electrical behaviors in La 1−x Sr x CoO 3. • Magnetic and electrical phase segregation in La 1− x Sr x CoO 3 around x = 0.3. • A magnetic-order change from magnetic long-range order to short-range one as x ≥ 0.3. • A careful review of critical behavior studies of perovskite cobaltites studied previously. Abstract We have carefully studied the relation between the critical and electrical behavior of rhombohedral La 1−x Sr x CoO 3 (x = 0.2–0.5) compounds prepared by solid-state reactions. The results obtained from analyzing M (T , H) data indicate that all compounds undergo a second-order phase transition and the ferromagnetic-paramagnetic (FM-PM) transition temperature increases from approximate 182 K for x = 0.2 to 253 K for x = 0.5. Basing on the modified Arrott and Kouvel-Fisher techniques, scaling hypothesis, and critical isotherm analysis, we have determined the critical exponent values characteristic of magnetic order of La 1−x Sr x CoO 3 , with β = 0.361–0.489, γ = 1.021–1.346, and δ = 2.99–4.72. Interestingly, though all compounds are metallic ferromagnets, we have found the phase segregation in magnetic order as x > 0.3, where magnetic interactions tend to change from long-to-short-range FM order together with the absence of the insulating-like behavior at temperatures below 100 K. These phenomena are related to the spatial coexistence of multiple electronic and magnetic phases due to the changes in concentration of cobalt ions, spin-state transitions, and the existence of poor-hole anti-FM and hole-rich FM regions. [ABSTRACT FROM AUTHOR]

In this work, we present a detailed study on the magnetic property and critical behavior in the austenitic phase of Ni 43 Mn 46 Sn 8 X 3 alloys with X = Cr and In, which were prepared by an arc-melting method in an argon ambience. The M ( T ) curve of the Cr sample (X = Cr) exhibits a single magnetic phase transition at the Curie temperature of the ferromagnetic (FM) austenitic phase with T A C = 303 K. In contrast, the In sample (X = In) exhibits multiple magnetic phase transitions, including a magnetic phase transition from a FM state to weakly magnetic state at T M C = 165 K of the martensitic phase, a martensitic transition from the weakly magnetic to the FM austenite phase at T M-A = 259 K, and a magnetic phase transition from the FM to paramagnetic (PM) at T A C = 297 K of the austenite phase. Based on the Landau theory and M ( H ) data measured at different temperatures, we pointed that the FM-PM phase transitions around T A C in both samples were the second-order phase transition. Our results suggest an existence of the long-range FM interactions in the austenite phase. A small deviation from the mean-field theory of the critical exponents has been also observed pointing out an existence of the inhomogeneous magnetism that could be associated with the presence of the anti-FM interactions in these samples. Besides, their effective exponents β eff ( ε ) and γ eff ( ε ) have been also calculated. [ABSTRACT FROM AUTHOR]

La 0.6 Ca 0.4− x Ce x MnO 3 ( x = 0, 0.03, 0.06, and 0.09) compounds are fabricated by a solid-state reaction, and their structural, magnetic, and magnetocaloric properties are investigated. The Curie temperature at which a ferromagnetic–paramagnetic transition occurs decreases from 260 to 221 K as x increases from 0 to 0.09. The saturation magnetization also decreases with the increase of x . The experimental results for the magnetization with respect to the temperature and magnetic field are analyzed using the Banerjee criterion, revealing that all the samples undergo the second-order magnetic phase transition. The maximum magnetic entropy change measured at a magnetic-field span of 50 kOe, which occurs near the Curie temperature, slightly increases from 6.31 to 7.62 J/kg K as x increases from 0 to 0.09. [ABSTRACT FROM AUTHOR]

The magnetic Mn 3+ ions in La 0.7 Ca 0.3 MnO 3 are partially replaced by nonmagnetic Zn 2+ ions to form La 0.7 Ca 0.3 Mn 1−x Zn x O 3 compounds ( x =0.0, 0.06, 0.08, and 0.1), and their magnetic and magnetocaloric properties are investigated. The Curie temperature decreases drastically from 245 to 70 K as x increases from 0 to 0.1. An analysis using the Banerjee's criterion of the experimental results for magnetization as a function of temperature and magnetic field indicates that the first-to-second order magnetic phase transformation occurs at a threshold composition of x =0.06, which is further supported by the universal curves of the normalized entropy change versus reduced temperature. The maximum magnetic entropy change measured at a magnetic field span of 50 kOe, which occurs near the Curie temperature, decreases from 10.30 to 2.15 J/kg K with the increase of x from 0.0 to 0.1. However, the relative cooling power, an important parameter for practical applications, shows a maximum value of 404 J/kg at x =0.08, which is 1.5 times greater than that observed for the undoped sample. [ABSTRACT FROM AUTHOR]

In this work, we prepared nanocrystalline Fe 2 Mn 1− x Cu x Al ( x =0.0, 0.1 and 0.3) powders by the high energy ball milling technique, and then studied their critical properties. Our analysis reveals that the increase of Cu-doping concentration (up to x =0.3) in these powders leads to a gradual increase of the ferromagnetic–paramagnetic transition temperature from 406 to 452 K. The Banerjee criterion suggests that all the samples considered undergo a second-order phase transition. A modified Arrott plot and scaling analysis indicate that the critical exponents ( β =0.419 and 0.442, γ =1.082 and 1.116 for x =0.0 and 0.1, respectively) are located in between those expected for the 3D-Heisenberg and the mean-field models; the values of β =0.495 and γ =1.046 for x =0.3 sample are very close to those of the mean-field model. These features reveal the coexistence of the short- and long-range ferromagnetic order in the nanocrystalline Fe 2 Mn 1− x Cu x Al powders. Particularly, as the concentration of Cu increases, values of the critical exponent shift towards those of the mean-field model. Such results prove the Cu doping favors establishing a long-range ferromagnetic order. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties in Ni 50 Mn 50− x Sn x alloys with wide range of the Sn-concentration ( x =0–40) were investigated. The alloys were prepared by arc-melting and subsequently annealing at 850 °C for 4 h. The X-ray diffraction analyses manifest the formation of the crystalline phases (Ni 2 MnSn, NiMn, Ni 3 Sn 2 , Mn 3 Sn, and MnSn 2 ) in the alloys with various compositions and fabrication conditions. With increasing x , the saturation magnetization first increases from near zero (at x =10) to above 40 emu/g (at x =20) and then decreases to below 10 emu/g (at x =40) for both the as-melted and annealed cases. The martensitic–austenitic transition was observed in the alloys with a narrow range of x (13–15). The magnetic transitions in the alloy can be controlled by changing Sn-concentration. The alloy reveals both the positive and negative entropy changes with quite large magnitude (∆ S m >1 J/kg K with ∆ H =12 kOe) with appropriate compositions and annealing conditions. [ABSTRACT FROM AUTHOR]

Abstract: A detailed study of the properties of the ferromagnetic to paramagnetic transition in polycrystalline manganites La1−x Ca x MnO3 (x=0.2, 0.3, 0.4) is presented. The first order transition in La0.7Ca0.3MnO3 is bordered by second order transitions in the neighboring La0.8Ca0.2MnO3 and La0.6Ca0.4MnO3 compositions. Analysis of the Landau–Lifshitz coefficients obtained from Arrott plots showed that while b(T) is uniformly negative in La0.7Ca0.3MnO3, it changes from positive to negative values in different magnetic field ranges for La0.8Ca0.2MnO3 and La0.6Ca0.4MnO3, indicating that the behavior cannot be described within a single model under the application of a strong field. The Kouvel–Fisher procedure performed on the samples with continuous transitions over different ranges of fitting field confirmed tricritical exponents in La0.6Ca0.4MnO3 but revealed that the critical exponents obtained for La0.8Ca0.2MnO3 depend strongly on the choice of field range, shifting from values consistent with short range (3D Heisenberg/3D Ising) interactions to those approaching the tricritical mean field model. This observation is attributed to the influence of magnetic field on the coexistence of energetically close double-exchange and superexchange ferromagnetic interactions in La0.8Ca0.2MnO3. [Copyright &y& Elsevier]

Abstract: A new kind of composite material consisting of parallel Co-based ferromagnetic microwires embedded in a polymer matrix was designed and produced for high-performance sensor applications. A great enhancement of the giant magnetoimpedance (GMI) effect and its field sensitivity was achieved in these composite materials. It was found that the GMI effect strongly increased with increasing number of ferromagnetic microwires. At a given frequency of 10MHz, the GMI ratio and its field sensitivity reached the highest values of 450% and 45%/Oe for the composite containing four microwires when compared with those of 14% and 1%/Oe for that containing one microwire. This indicates that the newly developed composite material is very promising for high-performance GMI sensor applications. It was revealed that the increase of the GMI effect in the composite sample was attributed to the decrease of electrical resistance and the increase of effective permeability. An increase of GMI effect with reducing microwire length was also observed and attributed to decrease of the electrical resistance. [Copyright &y& Elsevier]

Abstract: The critical exponents provide important information concerning the interaction mechanisms near the paramagnetic-to-ferromagnetic transition. In this paper, we present a thorough study of the critical behavior of a La0.9Pb0.1MnO3 polycrystalline sample by analyzing isothermal magnetization data. We determined the Curie temperature and the critical exponents (, , and ). With these exponents, we could successfully fit the scaling equation of state , where , f + for and f − for are regular scaling functions. We found that, at , β was close to the predicted value for the mean-field theory, whereas the value for γ was close to that for the Heisenberg model. We conjecture this feature originates from ferromagnetic clusters existing at wide ranging temperatures including even above T C. This conjecture was confirmed by electron paramagnetic resonance spectra around the Curie temperature. [Copyright &y& Elsevier]

Abstract: The magnetoimpedance of Fe76.5− x Cr x Si13.5B9Nb3Au1 (, 2, 3, 4, 5) alloys has been measured to investigate the influence of crystallization process on the soft magnetic properties and magnetic anisotropy after thermal treatment. Annealing performed at 540 and 550°C for 30min in a vacuum indicated that ultrasoft magnetic properties of nanocomposite materials are obtained. The magnetoimpedance ratio (MIR) and incremental permeability ratio (PR) measurements show that the maximum values of MIR and PR increase drastically in the heat-treated samples. It means that the samples are softened by nanocrystallization. The PR curves become narrower and sharper due to the decrease of anisotropy. The MIR behavior related with the softness of magnetic properties of heat-treated samples and the incremental PR strongly changes with external magnetic field. [Copyright &y& Elsevier]

Abstract: Amorphous ribbons Fe73.5− x Mn x Si13.5Nb3Cu1 (x=1, 3, 5) were prepared by rapid quenching on a single rotated copper wheel. The X-ray patterns show that the as-cast samples are amorphous. The measurements of thermomagnetic curves indicated that the Curie temperature of the amorphous phase of the samples decreased with increasing Mn content. The optimal heat treatment was performed at T a=535°C for 1h and showed that the ultrasoft magnetic properties of nanocomposite materials were obtained. The frequency dependence of magnetoimpedance was measured in the frequency range of 1–10MHz and at a fixed current of 10mA. The correlation between the MI effect and the soft magnetic properties is discussed. [Copyright &y& Elsevier]

Abstract: The magnetization behaviors have been analyzed for amorphous alloys. An amorphous phase was formed after quenching by melt spinning with a copper wheel with a surface speed of 30m/s. The magnetic properties of the ribbons were measured by vibrating sample magnetometer. The Curie temperature increases with increasing Y concentration ( to 10). Temperature dependence of the entropy variation was calculated from the isothermal magnetization. The maximum of was found to appear in the vicinity of the Curie temperature of the amorphous phase. Their values are 1.22, 0.89 and 1.12J/kgK at , 5 and 10, respectively. [Copyright &y& Elsevier]

Abstract: The super-giant magneto-impedance (SGMI) effect in an LC-resonator consisted of a glass-coated amorphous CoBSiMn microwire was studied. The sudden changes of magnetoimpedance at near the resonance frequency were observed, and the maximum ratio of SGMI reached as much as 400,000% in the experiment by precise tuning frequency at the resonance frequency. [Copyright &y& Elsevier]

Abstract: Effect of annealing on the soft magnetic properties of Fe73.5Si13.5B9Nb3Au1 amorphous ribbon has been investigated by means of structure examination, magnetoimpedance ratio (MIR) and incremental permeability ratio (PR) spectra measured in the frequency range of 1–10MHz at a fixed current of 10mAX-ray diffraction analysis showed that the as-cast sample was amorphous and it became nanocrystalline under a proper heat treatment. When annealing amorphous alloy at 530°C for 30, 60, 90min, soft magnetic properties have been improved drastically. Among the samples investigated, the sample annealed at 530°C for 90min showed the softest magnetic behavior. The MIR and PR curves revealed the desirable changes in anisotropy field depending upon annealing. [Copyright &y& Elsevier]

Abstract: The magnetization behavior has been analyzed for Gd1− x B x (x=0, 0.06, 0.09, 0.12) alloys which were prepared by conventional arc-melting method. The Curie temperature is very similar to B concentration. A large magnetic entropy change ΔSM , which is calculated from H vs. M curves associated with the ferromagnetic–paramagnetic transitions, has been observed. The maximum ΔSM for an applied field of 1.5T is 4.36, 4.08, 4.00, and 3.98J/kgK for x=0, 0.06, 0.09 and 0.12, respectively. Adiabatic temperature change ΔT ad is measured directly by a homemade cryostat. The maximum values for an applied field of 2T are 4.26, 3.86, 3.81, 3.86K for x=0, 0.06, 0.09 and 0.12, respectively. [Copyright &y& Elsevier]

Abstract: We report unconventional oscillatory tunnel magnetoresistance as a function of applied bias in the magnetic tunnel junction with the Al2O3 barrier. We attribute this feature to the inhomogeneity of the potential barrier structure. Ferromagnetic grains inside the potential barrier are formed at the technological stage. In this case, the TMR oscillation occurs due to the discrete charging effect that is well known as the Coulomb blockade. [Copyright &y& Elsevier]

Abstract: A thorough study of electron paramagnetic resonance (EPR) spectra of La0.5Sr0.5Co1− x Fe x O3 () compounds has been made. It is shown that, in the paramagnetic region, the EPR signal decreased considerably with increasing Fe-doped content. Cluster-glass (CG) behavior for compositions was realized near the phase transition temperature T C, but almost disappeared with further iron addition. This feature is a direct consequence of the magnetic frustration of random competing interactions, namely the ferromagnetic Co3+–Co4+ double-exchange interactions and the antiferromagnetic interactions like Co–O–Fe and Fe–O–Fe. For compositions, spin-glass (SG) behavior was observed and, this phase emerged and competed strongly with the CG phase. The results obtained from the EPR spectra are consistent with those obtained from the magnetization and resistivity measurements. [Copyright &y& Elsevier]

We present here the results of a detailed investigation on magnetic and transport properties of La0.5Sr0.5Co1-xFexO3 (x=0, 0.1) compounds. It is shown that the Curie temperature (TC) decreases slightly and the resistivity increases, even with a very small extent of Fe substitution. There was an evident coexistence of cluster glass (CG) and spin glass (SG) behaviors for x=0 composition. The Fe substitution induced additional antiferromagnetic Fe–O–Fe interactions that suppress strongly the ferromagnetism and conductivity, thus causing a phase separation for x=0.1 composition. We also figure out the nature of CG and SG behaviors and the influence of Fe doping on magnetic and transport properties of such a cobaltite system relying on electron paramagnetic resonance spectra. [Copyright &y& Elsevier]

• Magnetocaloric and magnetic behaviors of La 1-x Ba x CoO 3. • Short-range magnetic order existing in La 1-x Ba x CoO 3. • Possible reason of a second-order phase transition in La 1-x Ba x CoO 3. • Review the magnetocaloric behaviors of reported perovskite-type cobaltites. The magnetocaloric effect in the R- 3 c rhombohedral La 1-x Ba x CoO 3 samples (x = 0.2–0.4) prepared by the mechanical milling and ceramic methods has been studied through the dc magnetization measurements. The results have revealed the magnetic phase-transition temperature (T C) changing from 185 to about 200 K when × changes from 0.2 to 0.4. Around T C , the samples show a large change in the magnetic entropy (Δ S m). The value of Δ S m depends on both x and the applied-field magnitude. Under an applied field H = 30 kOe, the maximum magnetic-entropy changes are about 1.1, 1.7 and 1.6 J/Kg⋅K for x = 0.2, 0.3 and 0.4, respectively, corresponding to the relative cooling power ranging between 63 and 73 J/kg. Our studies have also found La 1-x Ba x CoO 3 exhibiting a second-order phase transition and short-range magnetic order. We suggest that short-range order is related to the interaction competition between two ferromagnetic and anti-ferromagnetic phases due to the coexistence of Co3+ and Co4+ ions. [ABSTRACT FROM AUTHOR]

Abstract: We studied the magnetic entropy change (ΔS m) of the perovskite manganites La0.7Ca0.3− x Sr x MnO3 (, 0.135, and 0.15). Effect of orthorhombic–rhombohedral structural transition, coinciding with the ferromagnetic–paramagnetic (FM–PM) phase transition, on the ΔS m is observed. The structural transition causes the double-step decrease of magnetization with temperature and widens the magnetic transition, leading to splitting of ΔS m into two peaks and also decrease in the overall values of ΔS m. [Copyright &y& Elsevier]

Abstract: We studied electrical and magnetic behaviors of polycrystalline samples of Nd0.7Sr0.3MnO3 prepared by the solid-state reaction method at 1300°C for 10, 20, 30, 40, and 80h. Magnetization M(T), resistivity ρ(T) and X-band electron paramagnetic resonance (EPR) measurements were carried out. Experimental results showed that the Curie temperature T C decreased considerably with increasing the annealing time t a from 10 to 30h, but became unchanged with t a>30h. The insulating-metallic transition was observed at T MI. Spin-dynamic processes in the ferromagnetic and paramagnetic regimes were recorded by EPR. Electrical conductivity and the EPR linewidth (ΔH) versus temperature were analyzed by means of the adiabatic hoping motion of small polarons. [Copyright &y& Elsevier]

Abstract: The switching characteristics of magnetic tunnel junctions (MTJs) comprising amorphous ferromagnetic CoFeSiB free layer have been investigated. CoFeSiB was used for the free layer to enhance the switching characteristics. The typical junction structure was Si/SiO2/Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlO x /CoFeSiB (t)/Ru 60 (in nm). CoFeSiB has low saturation magnetization (M s) of 560emu/cm3 and high anisotropy constant (K u) of 2,800erg/cm3. These properties caused low coercivity (H c) and high sensitivity in MTJs. It was also confirmed in submicrometer-sized elements by micromagnetic simulation based on the Landau–Lisfschitz–Gilbert equation. By increasing CoFeSiB free layer thickness, the switching characteristics became worse due to increase of the demagnetization field. [Copyright &y& Elsevier]

Abstract: Influences of oxygen-partial pressure and annealing on the electrical and magnetic properties of CoFeAlO thin films were systematically investigated by means of resistivity, permeability, magnetization and ferromagnetic resonance (FMR) measurements. It was found that, with increasing oxygen-partial pressure or under annealing, the electrical resistivity of the film increased and the magnetic softness decreased, which is attributed to the microstructural change of the film. Interestingly, an as-deposited Co45.30Fe20.65Al19.34O14.71 film was found to exhibit an inverted hysteresis loop with negative coercivity, and this peculiar phenomenon disappeared upon effects of oxygen-partial pressure and annealing. It was also found that the as-deposited films owned a narrow FMR line width that increased with increasing oxygen-partial pressure or under annealing. [Copyright &y& Elsevier]

Abstract: We studied electron spin resonance (ESR) spectra of La0.7A′0.3MnO3 (A′=Sr, Ba, Pb, and Cd) perovskites in a large range of temperature, from their Curie temperature to ∼500K. Asymmetrical EPR signals at temperatures , due to FM correlations, became Lorentzian at , where T min is the temperature corresponding to the narrowest ESR linewidth. The ESR linewidth vs. temperature, ΔH(T), in the region well fits to the model of adiabatic hopping motion of small polarons , where E a and k B are the activation energy and the Boltzmann factor, respectively; ΔH 0 and a are constants. It is worth noticing that, in this temperature range, the Lande factor g for the samples is about 2.00, indicating spin–spin interaction among electrons of Mn3+ and Mn4+ ions playing an important role. [Copyright &y& Elsevier]

Abstract: The magnetization behaviors have been analyzed for amorphous Fe73.5− x Cr x Si13.5B9Nb3Au1(,3,5) alloys. An amorphous phase was formed after quenching by melt spinning with a copper wheel surface speed of 30m/s. The structure analysis of as-cast was performed using X-ray diffractometer. The magnetic properties of the ribbons were measured by VSM. The Curie temperature is decreased from 629 to 491K with increasing Cr concentration (). Temperature dependence of the entropy variation was calculated from the isothermal magnetization. The maximum of was found to appear in the vicinity of the Curie temperature of the amorphous phase. The value is 1.7, 1.13 and 0.94J/kgK at , 3, and 5, respectively. [Copyright &y& Elsevier]

Abstract: Magnetotransport properties, magnetization, AC susceptibilities and electron spin resonance (ESR) were measured to investigate internal spin dynamics of cobaltites La1− x Sr x CoO3 (). Semiconducting behavior for and semiconducting-metallic transition for at ∼120K were observed. With increasing Sr doping, the Curie temperature (T C) increases. The spin-glass and cluster-glass behaviors were confirmed through the frequency-dependent AC susceptibility. ESR spectra of the samples in the temperature range studied could be divided into three regimes corresponding to different linewidths. This feature is due to both the presence of an anisotropic field arising from ferromagnetic clusters and the variation of spin-state transitions of Co ions. Lorentzian ESR signals at temperatures TT min. In a fashion similar to manganites, the peak-to-peak ESR linewidth vs. temperature, ΔH pp(T), for samples has a minimum value at temperature . To explain the physical mechanisms occurring in the samples, resistivity, AC susceptibility and ΔH pp(T) data were analyzed in detail. [Copyright &y& Elsevier]