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Ordered FePt film is attractive for its very high perpendicular anisotropy. In the present study, we report different texture formation and mechanisms of ordering FePt films on MgO (100) single crystal (A) substrates and MgO (200) polycrystalline film formed on Si[O.sub.2]/Si (B) substrates with and without Si[O.sub.2] addition. Films with structure of [[0.24 nm Pt/0.25 nm Fe/0.21 nm Si[O.sub.2].sub.15] were deposited on 600[degrees]C substrates and subsequently treated by rapid thermal annealing. In the as-deposited state, FePt grain size was smaller and its degree of ordering was lower on substrate (B) than substrate (A) regardless of Si[O.sub.2] addition. Upon annealing, grain growth was more significant on substrate (A) than on substrate (B), and degree of ordering kept nearly constant. However, in the case of Si[O.sub.2] addition, upon annealing, grain growth was more significant on substrate (B) than substrate (A), and the ordering parameter increased on both substrates (A) and (B). This indicates ordering reaction is dominated by phase separation of Mg,O or MgO incorporated in FePt grains of the as-deposited states during the short time rapid annealing treatments. Different texture formation and grain size difference in the two different substrates will be discussed together with the mechanism of ordering in FePt films. Index Terms--FePt, MgO substrates, ordering mechanism, Si[O.sub.2] addition.

Fe top layers with a thickness [t.sub.Fe] between 1 and 15 nm were deposited on textured FePt(001)/Pt(001)/Cr(002) layers to study the associated exchange coupling effect and their switching behaviors. The deposition of a Fe layer does not change the crystalline structure of the FePt layer. Microstructural analysis reveals that the Fe(200) texture is formed epitaxially on the FePt(001) surface. When [t.sub.Fe] = 1 nm, the remanent coercivity ([H.sub.cr]) remains the same as that without a Fe top layer. The lack of reversible magnetization reveals that the Fe layer is thinner than the critical thickness; the strong coupling force throughout the whole Fe layer facilitates the cooperatively magnetic rotation of Fe and FePt layers. Significant exchange spring was observed in the sample with [t.sub.Fe] = 3 and 5 nm, reducing Her by 14% and 43% (the maximum reduction), respectively. The results are consistent with the theoretical prediction. As [t.sub.Fe] was increased up to 8 and 12 nm, the exchange spring effect disappeared. Although the two films exhibited similarly reduced Her values of about 1.5 kOe, the reduction of Her is caused by the tilt of the magnetic moments rather than the exchange spring. This incline of the moments is caused by the weakened exchange coupling and the complex domain structure. The magnetic reversal was further examined by measuring the variation in longitudinal and transverse magnetizations during magnetic field sweeping. The results suggest that at [t.sub.Fe] = 1 and 3 nm, the reversal occurs cooperatively in a single direction. As [t.sub.Fe] is increased to 5 and 8 nm, the moments switch randomly, in a manner that may be related to the increase in the density of the domain wall, observed by MFM. This work demonstrates the feasibility of reducing coercivity through exchange-spring mechanism and provides information on detailed magnetic reversal mechanism in perpendicular exchange coupled FePt. Index Terms--Exchange coupling, FePt thin films, magnetic reversal behaviors, perpendicular recording.

The dynamic behavior of a mixed spin-l/2 and spin-3/2 Ising model with a crystal-field interaction in the presence of a time-varying magnetic field on alternate layers of hexagonal lattice is studied by using the Glauber-type stochastic dynamics. We study time variations of the average magnetizations in order to find the phases in the systems, and the temperature dependence of the dynamic sublattice magnetizations and total magnetization to obtain the dynamic phase transition (DPT) points and dynamic compensation points, respectively, as well as to characterize the nature (continuous and discontinuous) of transitions. Dynamic phase diagrams are also calculated for both DPT points and dynamic compensation effects. According to values of Hamiltonian parameters, besides the paramagnetic (p), antiferromagnetic (af) and antiferrimagnetic (i) fundamental phases, the af + p, i + p and i + af mixed phases, and the compensation temperature or P- and L-types behavior in the Neel classification nomenclature exist in the system. Index Terms--Compensation, magnetic field effects, magnetic materials, magnetic recording.

Hot-pressed [Nd.sub.13.5][Fe.sub.77][Si.sub.1][B.sub.8] alloy compacts with various grain sizes ranging from approximately 50 nm to 200 nm were prepared using melt-spun material. The compacts were then subjected to die-upsetting. The effect of grain size in the hot- pressed compact on the texture in die-upset magnet was investigated. The effect of die-upset temperature on the texture in die-upset magnet was also investigated. Texture in the die-upset [Nd.sub.13.5][Fe.sub.77][Si.sub.1][B.sub.8] alloy samples decreased with increasing the grain size in the hot-pressed compact before the die-upsetting. This dependence of texture on the initial grain size could be explained by the unique texture formation mechanism of a stress-induced preferential grain growth via dissolution and precipitation. Texture of the die-upset sample was also influenced by the die-upsetting temperature. The samples die-upset at 700[degrees]C and 900[degrees]C had poorer texture compared to the samples die-upset at the temperature range of 750[degrees]C-850[degrees]C. The poor texture in the sample die-upset at lower temperature of 700[degrees]C was attributed to the less dissolution of the unfavorable [Nd.sub.2][Fe.sub.14]B grains and low fluidity of the liquid Nd-rich grain boundary phase. The poor texture in the sample die-upset at higher temperature of 900[degrees]C was explained by the reduced elastic modulus and the excessive grain growth of the [Nd.sub.2][Fe.sub.14]B grains. Index Terms--Hard magnetic materials, magnetic materials, magnets, permanent magnets.

The [La.sub.0.8][Ca.sub.0.2][Mn.sub.0.99][sup.57][Fe.sub.0.01][O.sub.3] sample was prepared by sol-gel method. The crystallographic and magnetic properties of [La.sub.0.8][Ca.sub.0.2][Mn.sub.0.99][sup.57][Fe.sub.0.01][O.sub.3] have been studied using x-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mossbauer spectroscopy measurements. The crystal structure of [La.sub.0.8][Ca.sub.0.2][Mn.sub.0.99][sup.57][Fe.sub.0.01][O.sub.3] was found to be orthorhombic (Pnma) structure with lattice constants [a.sub.o] = 5.486 [Angstrom], [b.sub.o] = 7.761 [Angstrom], and [c.sub.o] = 5.510 [Angstrom] at room temperature. The Curie temperature ([T.sub.c]) is determined to be 160 K by zero field coolded (ZFC) magnetization curve under 5 kOe applied field. The maximum value of magnetic entropy changes, [absolute value of [DELTA][S.sub.M]] is 1.25 J/kg x K at 157 K under 13 kOe applied field. Mossbauer spectrum at 4.2 K was fitted with two independent magnetic components of the magnetic hyperfine fields [H.sub.f,1] = 526 kOe and [H.sub.f,2] = 501 kOe. Mossbauer spectra show that the two well-resolved sextets show nearly equal intensities between them without any external fields. This unusual phenomenon provides direct evidence of the two-phase character of the metallic state in the mixed valence state of [La.sub.0.8][Ca.sub.0.2][Mn.sub.0.99][sup.57][Fe.sub.0.01][O.sub.3] powder. Index Terms--[La.sub.0.8][Ca.sub.0.2][Mn.sub.0.99][sup.57][Fe.sub.0.01][O.sub.3], magnetic refrigeration, magnetocaloric effect, Mossbauer spectra, sol-gel method.

Angular dependence of Gilbert's damping constant [alpha] for Ni-Fe(001) single-crystal thin films were investigated by employing Q-band (35 GHz) and X-band (9 GHz) ferromagnetic resonance analysis in terms of the specimen's crystal structure. The [alpha] for 10-nm-thick specimen had constant values of 0.006, which were estimated by the Q-band ferromagnetic resonance (FMR) spectra, when the spectra were measured with changing external field directions in the film plane and out of plane. The [alpha] for the Ni-Fe specimens did not depend on the crystal directions. The [alpha] values estimated by X-band FMR spectra were in good agreement with those by Q-band FMR spectra, when the magnetization of the specimens was saturated at the X-band resonance field. The [alpha] values were overestimated, when the magnetization was not saturated and the specimens had multidomain structures at the resonance field. Index Terms--Ferromagnetic resonance (FMR), Gilbert's damping constant, permalloy, Q-band, X-band.

Co epitaxial thin films were prepared on single-crystal MgO substrates of (100), (110), and (111) planes heated at 300[degrees]C by ultra high vacuum molecular beam epitaxy. The film crystal structure varies depending on the substrate orientation. On MgO(100) substrate, a Co(11[bar.2]0) epitaxial bi-crystalline film with an hcp structure is obtained. A Co(110) single-crystal film with an fcc structure is formed on MgO(110) substrate, whereas a Co(0001) single-crystal film with an hcp structure is grown on MgO(111) substrate. Co film growth on MgO substrates follows the Volmer-Weber mode. The in-plane magnetization properties reflect the magnetocrystalline anisotropy of bulk hcp-Co or fcc-Co crystal. The Gilbert's damping constants of these 40-nm-thick epitaxial Co films are determined. Index Terms--Co thin film, epitaxial growth, FMR, single-crystal substrate.

Co[Cr.sub.2][O.sub.4](CCO) materials show multiferroic effect that ferroelectricity and ferromagnetism co-exist. CCO film was deposited on Pt/Ti/Si/Si[O.sub.2] substrates by pulsed laser deposition (PLD). The CCO film were prepared using KrF(248 nm) excimer lasers and with a pressure of 100 mTorr, substrate temperatures of 700[degrees]C. The crystal structure was found to be oriented {111} planes by means of X-ray diffraction (XRD) with Cu radiation. The morphology of film has showed triangle shapes. The ferrimagnetic transition was observed at around 95 K, which was determined as Neel temperature and spiral magnetic transition temperature ([T.sub.s]) was 21.5 K, while the [T.sub.s] of bulk CCO was 28.0 K. We note that decreasing of [T.sub.s] in CCO films is closely related to the preferred orientation of {111} direction. Index Terms--Multiferroic, pulsed laser deposition, spiral magnetic transition.

We present the study on the structural and the magnetic properties of LiFeP[O.sub.4] and Li[Fe.sub.0.8] [Co.sub.0.2]P[O.sub.4]. The crystal structure was determined to be orthorhombic with space group Pnma by Rietveld refinement method. We have observed the increase in the lattice constants with [Co.sup.2+] ion substituted. The Mossbauer spectra of olivine LiFe[P[O.sub.4] and Li[Fe.sub.0.8][Co.sub.0.2]P[O.sub.4] have shown distorted line broadening below [T.sub.N]. In order to explain the observed line broadening, we have analyzed the Mossbauer spectra by considering the full Hamiltonian for the [sup.57]Fe nucleus, and both the magnetic dipole and the electric quadrupole interactions. Also, we have observed the anomalous change in the electric quadrupole splitting near the [T.sub.N]. Index Terms--Crystal field, Mossbauer spectroscopy, olivine structure.

The [Mn.sub.1-x][Co.sub.x][Fe.sub.2][O.sub.4] (x = 0.0, 0.5, 1.0) materials were prepared by the high-temperature thermal decomposition method and studied for its unique magnetic phenomena of magnetic nanoparticles. The crystal structure is found to be an inverse cubic spinel with a space group of Fd - 3m and the lattice constants ([a.sub.o]) of 8.432, 8.486, and 8.466 [Angstrom], respectively. The samples show magnetization ([M.sub.s]) of 54.2, 29.4, and 46.9 emu/g, respectively. Also, the coercivities ([H.sub.c]) of all samples are 32.4, 86.9, and 90.7 Oe, respectively. Mossbauer spectra of all samples were obtained at various temperatures. Mossbauer spectra show a ferrimagnetic state of six-line having the hyperfine field ([H.sub.hf]) values of 456, 472, and 475 kOe for the tetrahedral sites and 400, 422, and 430 kOe for the octahedral sites, respectively, which increases with doping Co concentration. Index Terms--Cobalt ferrite, high-temperature thermal decomposition (HTTD), manganese ferrite, Mossbauer spectroscopy.