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Short time relaxation effect in [Nd.sub.0.5][Sr.sub.0.5]Mn[O.sub.3] manganites was observed. The effect is manifested as negative peak of imaginary component of ac magnetic susceptibility near the point of first order phase transition. The effect is explained at the frame of Landau theory of phase transition, where the coexistence of metastable and stable phases is considered. Index Terms--Magnetic losses, magnetic susceptibility, relaxation processes.

The magnetization behaviors have been investigated for [La.sub.1-x][Pb.sub.x]Mn[O.sub.3] (x = 0.1, 0.2, 0.3) alloys. The Curie temperature increased from 195 to 352 K with increasing Pb concentration. A large magnetic entropy change ([DELTA] [S.sub.M]), which is calculated from H versus M curves associated with the ferromagnetic-paramagnetic transitions, has been observed. The maximum [DELTA] [S.sub.M] of [La.sub.0.8] [Pb.sub.0.2] Mn[O.sub.3] was 1.22 J/kg K at 294 K for an applied field of 1.5 T. Adiabatic temperature change ([DELTA][T.sub.ad]) was measured directly by a special cryostat. The maximum [DELTA][T.sub.ad] of [La.sub.0.7] [Pb.sub.0.3] Mn[O.sub.3] was 1.00 K at 352 K for an applied field of 2 T. Index Terms--Adiabatic temperature change, entropy change, magnetocaloric effect (MCE).

IrMn pinned spin-valve (SV) films with stacks of Ta-NiFe-IrMn-CoFe-Cu-CoFe-NiFe-Ta were prepared by dc sputtering onto thermally oxidized Si (111) substrates at room temperature under a magnetic field of about 100 Oe. The annealing cycle number and temperature dependence of the exchange-coupling field ([H.sub.ex]), magnetoresistance (MR) ratio, and coercivity ([H.sub.c]) were investigated. By optimizing the process of deposition and the post-thermal annealing condition, we obtained the IrMn-based SV films with MR ratio of 3.6%, [H.sub.ex] of 1180 Oe for the pinned layer. The [H.sub.ex] is stabilized after the second annealing cycle, and it is thought that this SV reveals high thermal stability. The [H.sub.ex] maintained its strength of 600 Oe in operation up to 240[degrees]C and decreased monotonically to zero at 270[degrees]C. Index Terms--Annealing cycle number, antiferromagnetic, exchange-coupling field, Ir-Mn pinned spin-valve film.

The structure and magnetic properties of Fe-[Si.sub.3][N.sub.4] thin films fabricated by a co-sputtering technique were studied by X-ray diffractometry and magnetometry. With increasing area fraction of [Si.sub.3][N.sub.4] pieces on Fe target magnetization of the films decreased due to reduced Fe content and reduced grain size of bcc crystalline phase. Temperature dependence and field dependence of magnetization of co-sputtered thin films can be explained by a mixture of two types of particles showing paramagnetism and ferromagnetism.

For amorphous [Co.sub.1-x][Ti.sub.x](X=0.13, 0.16, 0.21 at.%) thin films deposited by DC magnetron sputtering method ferromagnetic resonance experiments have been used to investigate the dependence of surface magnetic properties in according to annealing temperatures(150 [similar to] 225 [degrees] C). Spin wave resonance spectra for all annealing temperatures consist of several volume modes and one(or two) surface mode. It is suggested that both surfaces of the film have a perpendicular hard axis to the film plane(negative surface anisotropy). Also, the surface anisotropy [K.sub.s2] at substrate-film interface is varied slowly from -0.11 to -0.25 erg/[cm.sup.2] and the surface anisotropy [K.sub.s1] at film-air interface is varied from 0.16 to -0.53 erg/[cm.sup.2] with increasing annealing temperatures. We conjecture that the variation of surface anisotropy [K.sub.s1] is due to the increase of Co concentration resulted from Ti oxidation for low temperature annealing(150 [similar to] 200 [degrees] C) and the diffusion of Co atoms near the film surfaces for high temperature annealing (225 [similar to] 250 [degrees] C).

We have studied the magnetization behaviour and the temperature dependence of AC-susceptibility at very low fields (5mOe to 50mOe) of glassy [Fe.sub.91-x][Zr.sub.7][B.sub.2][Ni.sub.x] (X = 0, 5, 10, 15) alloy system. At zero Ni concentration our data suggests the existence of a spin-glass behaviour at temperature below 30 K. The addition of Ni drastically modifies the magnetic properties: the antiferromagnetic exchange coupling is reduced, the magnetic moment of Fe increases from 1.58 to 2.29[[Mu].sub.B] and [T.sub.C] increases from 230 to 478 K. Thus, substitution of Fe by Ni favours the increase of magnetic order in this system.

The magnetic property of supersaturated [Fe.sub.20][Co.sub.30][Cu.sub.50] solid solution, prepared by mechanical alloying, has been investigated by using magnetometry, Mossbauer spectroscopy and inelastic neutron scattering measurements. Magnetization measurement of the alloy could be analysed by ferromagnetism only. However, Mossbauer spectroscopy and inelastic neutron scattering experiment showed that not only ferromagnetic phase but also paramagnetic phase of about 12% coexist in the alloy. Spin wave stiffness constant obtained from the analysis of the temperature dependence of magnetization was similar to the value obtained from analysis of inelastic neutron scattering experiment.

It is shown that progressive crystallization of non-magnetostrictive Co-based metallic glass (VITROVAC 6030) leads to an increase of coercivity by more than three orders of magnitude. The mechanisms responsible for this phenomenon are interpreted showing that the main source for the giant increase of the coercivity is the pinning effect on the domain walls originating from the created crystallites of the size much smaller than the domain width (correlation length for ferromagnetic exchange interactions). It is also shown that gradually devitrified non-magnetostrictive metallic glass is an excellent model material for verification of Neel's theory describing the Rayleigh rule. Index Terms-Coercivity, nanocrystalline magnets, non-magnetostrictive metallic glass, Rayleigh rule.

Ce-substituted Yttrium Iron Garnet films have been epitaxially grown on (111)-oriented Gadolinium Gallium Garnet substrates by Pulsed Laser Deposition technique. X-ray diffraction measurements show epitaxial growth of the garnet film along its [111] axis. The films were grown at substrate temperature of 790 [degrees] C and various oxygen partial pressure varying from 10 to 100 mTorr. From the magnetic properties measured by VSM, we found that the fabricated (Ce[Y.sub.2])[Fe.sub.5][O.sub.l2] films have In-plane magnetization with no preferential easy direction in the plane. The saturation Faraday rotation values obtained from measurements at [Lambda] = 633 nm and room temperature are found to be dependent on the oxygen pressure, with the maximum value of 0.7 deg/[micro]m for the films grown at 50 mTorr. Index Terms--Ce-substituted Yttrium Iron Garnet, Pulsed Laser Deposition, Faraday rotation, Ferromagnetic Resonance.