Pinning Fields In Amorphous Materials

The stress and field dependence of the pinning field Hp of ribbons of the composition Fe73.5Cu1Nb3Si 13.5B9 and Co73.5Cu1Nb 3Si13.5B9 is compared with that of the coercivity HC. The similar character of HC(σ) and Hp(σ) indicates a strong correlation between these two properties. At higher external stresses HC(σ) and H p(σ) depend on a premagnetizing procedure. This can be explained assuming a different domain structure.731057275729New University of Lisbon,UNINOVA,Universiteit van Amsterda

Magnetic anisotropy and magnetic phase transitions in RFe(10)Mo(2) (R=Pr,Nd,Sm,Dy,Ho,Er,Tm)

RFe(10)Mo(2) (R=Pr, Sm, Nd, Dy, Ho, Er, Tm) intermetallics were investigated by studying the temperature or field-induced spin-reorientation transitions (SRT's). The temperature dependence of the magnetic anisotropy field was determined by means of the singular point-detection technique for the polycrystalline samples of YFe10Mo2, NdFe10Mo2, DyFe10Mo2, and ErFe10Mo2. Main emphasis was given to the theoretical analysis of the magnetic anisotropy constants and the magnetic phase transitions. The temperature dependences of the rare-earth anisotropy constants were calculated using the single-ion model within linear theory. The applicability of the linear theory of the R anisotropy is discussed. It is shown that the accuracy of this theory increases considerably with increasing temperature. Fitting the experimental data, a set of the crystal field and exchange field parameters for the rare-earth R(3+) ions was deduced. The observed SRT's and first-order magnetization processes (FOMP's) were explained and classified. FOMP-like transitions in PrFe10Mo2, HoFe10Mo2, and ErFe10Mo2 were identified. The temperature dependence of the FOMP fields was calculated for HoFe(10)MO(2) and ErFe10Mo2. The physical origin of a low-temperature anomaly in the magnetization process is discussed for SmFe10Mo2. The spin-reorientation transitions:in ErFe10Mo2 and TmFe10Mo2 are determined to be of first order with a discontinuous jump of the magnetization. The SRT's detected in NdFe10Mo2 and DyFe10Mo2 are of second order. The calculated temperature dependences of the anisotropy fields for DyFe10Mo2 and NdFe10Mo2 are in good agreement with the experimental data over a wide temperature range. FOMP's are predicted at low temperatures for NdFe10Mo2, DyFe10Mo2, and TmFe10Mo2.55138038

Description of magnetic anisotropy and spin-reorientation transitions in NdFe12-xMox and NdFe12-xMoxN (x=1,0, 2.0, 3.0)

NdFe12-xMox and NdFe12-xMoxN (x = 1,2,3) were investigated by studying the anisotropy field and the temperature or field-induced spin-reorientation transitions. The temperature dependence of the magnetic anisotropy field was determined by means of the singular-point-detection technique for polycrystalline aligned samples. A theoretical explanation of the magnetic anisotropy and the magnetic phase transitions is given. The temperature dependencies of the rare-earth anisotropy constants were calculated using the single-ion model within linear theory. Fitting the experimental data, a set of crystal-field and exchange-field parameters for Nd3+ ions was deduced. A first-order spin-reorientation transition from uniaxial to conical phase and a type-2 first-order magnetization process in the perpendicular field are calculated for NdFe11Mo. A canted magnetic structure and a type-1 first-order magnetization process in the axial field are predicted for NdFe12-xMoxN. A change of rare-earth anisotropy after nitrogenation was explained by a bonding charge and a superposition model. The calculated temperature dependence of the anisotropy fields in NdFe12-xMoxN is in good agreement with the experimental data over a wide temperature range. (C) 1996 American Institute of Physics.8031659166

The Influence Of Quenching Rate On Magnetic Properties Of Amorphous Ribbons

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Five sets of amorphous ribbons of the composition Fe73.5Cu 1Nb3Si13.5B9 produced with different quenching rates (QR) were studied in order to verify the influence of the topological disorder on magnetic properties. For this purpose several magnetic methods were applied. Significant differences have been found between the results of magnetic disaccommodation He·Δμ/μ, pinning field Hp and stress dependence of the magnetic permeability μ/μ0(σ) of as-cast materials produced at different QR. The values of He·Δμ/μ and Hp are directly proportional to the disorder degree of the samples. The μ/μ0(σ) curves display broad maxima, which are found to be related to the quenched-in stresses. In contrast with these results, no significant effects of the amorphous structure on the Curie temperature and Mössbauer spectra were found, because other parameters are dominating.7310660366052011/01071-3; FAPESP; São Paulo Research FoundationFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Domain structure dynamics of amorphous Fe64Co21B15 and Co77B23 ribbons studied by three-dimensional neutron depolarization

Relaxation phenomena related to domain structure dynamics in amorphous ferromagnetic Fe64Co21B15, and Co77B23 samples were studied by time-resolved three-dimensional neutron depolarization and a conventional magnetic induction technique. Different initial domain structures were induced either by applying external stresses or by stress annealing. A theoretical model was developed to describe the observed time dependence of neutron depolarization upon passage through such samples. It is shown that the domain structure approaches the equilibrium state with stable domain wall positions at a rate that depends essentially both on the sample composition and on the induced magnetic anisotropy. (C) 1999 American Institute of Physics. [S0021-8979(99)01402-4].8521043104

Magnetic Behaviour of Disordered Ising Ferrimagnet in High Magnetic Field

The magnetic behaviour of a disordered ferrimagnetic system Ap B1-p where both A and B represent the magnetic atoms with respective spin SA = 1/2 and SB = 1 in presence of high magnetic field is treated theoretically.Assuming the magnetic interaction can be described through Ising Hamiltonian the approximate free energy is obtained using the cluster-variational method. The field dependence of the magnetization is then obtained for different concentration p and exchange parameters (JAA, JBB and JAB). For p = 0.5,the magnetization M in ferrimagnetic state and in absence of compensation temperature Tcm vanishes at TC.Field induced reversal of M is found at switching temperature TS (<TC) which is decreasing function of field H.A maximum in M is found above TS and the maximum value of M increases with field.In ferrimagnetic state M increases almost linearly at high H region. For system with large ferromagnetic JAA,the compensation temperature Tcm is increasing function of JBB and JAB .The decrease in compensation temperature is linear at small field and tends to saturate at higher field.The sharpness of the magnetization reversal is increased with H.For fully compensated state of the system with p = 2/3,the magnetization in presence of H also exhibits switching behaviour at TS .For p = 0.2 the field induced reversal of magnetization occurs more sharply.The orientational switching of the sublattice magnetization MA and MB with field increases the Zeeman energy and is the origin of magnetization reversal at TsComment: 12 pages,9 Figure

MAGNETIC-PROPERTIES OF AMORPHOUS CO75-XFEXSI15B10(0-LESS-THAN-X-LESS-THAN-50)

On amorphous ribbons of the composition Co75-xFexSi15B10 (0 less-than-or-equal-to x less-than-or-equal-to 50) the Curie temperature T(C), the saturation magnetization and the magnetostriction constant lambda(S) were determined. The concentration dependence of T(C) was analysed using a molecular field model. The concentration and temperature dependence of the saturation magnetization was analysed assuming a superposition of the Fe- and Co-moments respectively. Lambda(S)(x, T) was analysed assuming the existence of a single and a two ion term.1164167115415

Magnetic Properties Of Amorphous Co75-xfexsi15b10 (0 &lt; X &lt; 50)

On amorphous ribbons of the composition Co75-xFexSi15B10 (0 ≤ x ≤ 50) the Curie temperature TC, the saturation magnetization and the magnetostriction constant λS were determined. The concentration dependence of TC was analyzed using a molecular field model. The concentration and temperature dependence of the saturation magnetization was analysed assuming a superposition of the Fe- and Co-moments respectively. λS(x, T) was analysed assuming the existence of a single and a two ion term. © 1992.1161-2154158Madurga, Vázquez, Hernando, Nielson, (1984) Solid State Commun., 52, p. 701Hernando, Influence of the Tensile Stress on the Magnetostriction Resistivity and Magnetic Anisotropy of Co-Rich Metallic Glasses. TSRO and CSRO Correlation (1988) Physica Scripta, 24 T, p. 11Herzer, (1986) Intern. Conf. Soft Magn. Mater., 7, p. 335Hilzinger, Herzer, Wengert, (1985) Rapidly Quenched Metals, 5, p. 1263. , S. Steeb, H. Warlimont, North-Holland, AmsterdamNarita, Yamasaki, Fukunaga, Measurement of saturation magnetostriction of a thin amorphous ribbon by means of small-angle magnetization rotation (1980) IEEE Transactions on Magnetics, p. 435Fujimori, Kikuchi, Obi, Masumoto, (1976) Sci. Rep. Res. Inst. Tohoku Univ., 26 A, p. 36Xianyu, Ishikawa, Fukunaga, Watanabe, (1985) J. Phys. F, 15, p. 1799Kouvel, (1969) Magnetism and Metallurgy, p. 523. , A.E. Berkowitz, E. Kneller, Academic Press, New YorkLuborsky, (1980) Ferromagnetic Materials, 1, p. 494. , E.P. Wohlfarth, North-Holland, AmsterdamO'Handley, (1978) Phys. Rev. B, 18, p. 93