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A low temperature ordering of L[1.sub.0] FePt phase was directly achieved by using 2-MeV He-ion irradiation without conventional post-annealing. The coercivity greater than 5700 Oe can be obtained by using ion-irradiation heating at temperature as low as 230[degrees]C. The high beam-current-density results in direct beam heating on samples. In addition, the irradiation-induced heating process provides efficient microscopic energy transfer and creates excess point defects, which significantly enhances the diffusion and promotes the formation of the ordered phase. Index Terms--Beam heating, FePt, irradiation, ordering.

The effects of Co insertion at the interface of CoCrPtB-Ru-CoCrPtB AFC media are investigated. Although the exchange coupling constant J can be increased by inserting Co, undesired magnetic properties are observed including reduction of the switching field of the stabilizing layer or reduction of coercivity of the recording layer. We propose a new antiferromagnetically coupled structure with a laminated stabilizing layer composed of CoCrPtB-(Ru or CoCr)-Co, in which Co remains at the interface to enhance J and a nonmagnetic layer Ru or CoCr is used for suppressing interaction between Co and lower CoCrPtB layer. The coercivity of the laminated stabilizing layer decreased and the switching field increases with increasing thickness of Ru or CoCr. Consequently, the insertion of Ru or CoCr can make the magnetization reversal of the stabilizing layer easier. Index Terms--Antiferromagneticany coupled (AFC), CoCr, Ru, switching field.

Severe Ga accumulation at the back contact is regarded as one of the major limiting factors for high efficiency Cu(In,Ga)Se2 (CIGSe) solar cells fabricated by the sequential process. The Ga deficiency near the front surface of absorber leads to the reduction of open‐circuit voltage; however, controlling the Ga grading is quite challenging during the selenization process. Herein, the tuning of Ga profile is demonstrated by forming the ordered vacancy compound (OVC) phase at the beginning of selenization process under high Se partial pressure (PSe) with the precursor composed of a relatively high In content. The OVC phase formed with a columnar structure promotes Ga diffusion through Cu vacancies, resulting in Ga increase at the front side of CIGSe. However, high PSe also increases the thickness of MoSe2, significantly raising the series resistance. Thereby, a 5 nm TiN layer is deposited on top of Mo to suppress the formation of MoSe2. In addition, the extra Na‐contained precursor is added to increase the carrier concentration because the TiN layer also blocks the Na outdiffusion from the substrate. By controlling PSe, interlayer TiN thickness, and carrier concentration, a 16.04% record high efficiency of CIGSe solar cells (sulfur‐free) via elemental Se source is achieved. [ABSTRACT FROM AUTHOR]

Single‐layered MoS2 is a naturally stable material. Integrating spin, valley, and circularly polarized photons is an interesting endeavor to achieve advanced spin‐valleytronics. In this study, room‐temperature ferromagnetism in MoS2 induced by the magnetic proximity effect (MPE) of yttrium iron garnet (YIG) and the antiferromagnetic coupling at the interface is demonstrated. Insulating YIG without charge carriers is an excellent magnetic candidate featuring a long spin diffusion length and remarkable surface flatness, enabling long‐range magnetic interactions with MoS2. Spin‐resolved photoluminescence spectroscopy and magnetic circular dichroism (MCD) reveal that the spin‐polarized valleys of MoS2 can achieve sustained ferromagnetism even at room temperature. The bandgap‐sensitivity of MCD further demonstrates the extent of antiferromagnetic coupling between the MPE‐induced moments of MoS2 and YIG. This work provides a layer‐selected approach to study magnetic interactions/configurations in the YIG/MoS2 bilayer and highlights the role of MoS2 in achieving the MPE toward high temperature. [ABSTRACT FROM AUTHOR]

Pseudo-antiferromagnetically coupled (AFC) structure media are fabricated by replacing the ferromagnetic layers adjacent to the Ru layer with nonferromagnetic layers in the AFC media. Lattice mismatching is manipulated by changing Ru to RuCo(Cr) alloys. The medium without Ru shows narrower PW50 and higher signal-to-noise ratio (SNR) than the pseudo-AFC medium with Ru. After replacing Ru with RuCo or RuCoCr, the PW50 and SNR are nearly constant when the thickness of Ru alloy is in the range of 0 to 8 [Angstrom]. X-ray data show that better Co (11.0) texture is found in the pseudo-AFC media with Ru alloy layer than Ru layer. Transmission electron microscope images indicate that the Ru layer enlarges the grain and broaden its distribution. Index Terms--AFC media, grain size, lattice matching, pseudo-AFC structure, PW50, signal to noise.

The addition of 2 % Zr into the CrMo underlayer reduced the grain size of the recording layer to 5.33 nm and achieved a narrow distribution of grain size. The addition of 5% Mn into the CrMo underlayer enhanced the crystallographic texture and coercivity. To obtain both advantages of Zr and Mn doping effects, the Zr and Mn doped double underlayer were introduced in longitudinal media. The magnetic properties and microstructures of the recording layers on CrMoMn-CrMoZr and CrMoZr--CrMoMn double underlayers mainly depended on the underlayer adjacent to the CoCr layer, whereas the underlayer on NiP further modified the characteristics of the recording layers. By combining the CrMoMn and CrMoZr double underlayers, longitudinal media revealed enhanced coercivity, small intergranular coupling, and a narrow distribution of grain size. Index Terms--CrMoMn underlayer, CrMoZr underlayer, double underlayer, grain size, intergranular coupling, longitudinal media.

The effects were investigated of carbon ion dose on the exchange field and GMR ratio of irradiated PtMn-based spin valves. The exchange field increases with increasing dose in the low ion-dose-regime, which is attributed to the increase in PtMn(C) formation. The maximum enhancement of the exchange field can be as large as 50% for the ion dose of 2.0 x [10.sup.14] ions/[cm.sup.2]. The reduction of the exchange field in the high-dose regime is probably due to the intermixing or carbon residue at the interface. The giant magnetoresistance (GMR) ratio monotonically decreases with increasing carbon dose. Ion irradiation shows different effects on fcc and fct PtMn samples. By proper annealing prior to irradiation, we can obtain a large enhanced exchange field and a reasonably good MR ratio. Index Terms--Exchange field, giant magnetoresistance (GMR), ion irradiation, PtMn-based spin valves.

We have studied the temperature effect on magnetic properties in (001) epitaxial Co-NiMn. The interfacial exchange coupling in Co-NiMn not only induces a unidirectional anisotropy but also a uniaxial anisotropy. Double shifted hysteresis loops could be found along the hard axis, and used to accurately determine the anisotropy constants using the coherent rotation model. The cubic anisotropy of Co decreases monotonically with increasing temperature, while the interface-induced uniaxial anisotropy decreases with increasing temperature up to 180[degrees]C, and then increases with further increasing temperature. A mechanism explaining the enhancement of interface-induced uniaxial anisotropy and coercivity at temperatures above 180[degrees]C is proposed. Index Terms--Anisotropies, coercivity, double shifted hysteresis loop, induced uniaxial anisotropy, thin film, vibrating sample magnetometer, (001) epitaxial Co-NiMn.

It has been possible to produce ferrimagnetic spin valves with the magnetization perpendicular to the film planes. For samples made up of both transition-metal-rich (or both rare-earth-rich) TbFeCo and GdFeCo, negative giant magnetoresistance values were gained.

Inserting the nano-oxide layer at the Ta/Co interface in the FeMn-based top spin valves makes it possible to increase the magnetoresistance ratio by 35%. The increase in magnetoresistance is accompanied by a rise in resistance change and a fall in sheet resistance.

Research into in-plane magnetic anisotropy in Co films epitaxially grown on NiMn (001) films is presented. It was found that exchange coupling in NiMn/Co induces a unidirectional anisotropy and a uniaxial anisotropy.

Research into the correlation between the exchange field of NiFe/NiMn and the phase transformation of NiMn is presented. The exchange field between NiFe and NiMn was found to increase almost linearly with a rising order volume fraction of NiMn.

Research into the exchange field and domain configurations in patterned polycrystalline and (100) NiO/NiFe films is presented. It is concluded that the size dependence observed in (100) patterned films can be explained by Malozemoff's model, in which the domains of NiO are physically reduced by patterning.

A study was conducted to analyze the orientation influence on the exchange field in the sputtered NiFeO/NiFe system. In-plane textured MgO films were utilized as structural templates to change the crystalline orientations of NiFeO. The films were prepared on 2200 Angstrom amorphous Si3N4/Si(100) substrates. Experimental results indicated that the exchange field is affected by the out-of-plane alignment related to th plane anisotropic energy of NiFeO.

We present a study concerning the unexpectedly large coercivity increase and associated magneto-structural properties of CoxNi1-x patterned arrays. An increase in x led to an face-center-cubic (FCC)→hexagonal-close-packed (HCP) transition in CoxNi1-x arrays, accompanied by a 6-fold increase in coercivity and strong 3d exchange interactions probed by x-ray magnetic circular dichroism. Sum-rule analysis revealed that orbital moment involved very little in the variable coercivity and magnetic anisotropy; this is distinct from other nanostructures displaying variable coercivity. The sharp rise in coercivity can be attributed to the geometrical confinement of the arrays, causing the microstructure of the nano-clusters to switch magnetization reversal mechanism from fanning to coherent with increasing x, based on the chain-of-spheres model. First-order-reversal curves revealed that the FCC and HCP arrays comprised both soft and hard ferromagnetic components; however, the soft component of the FCC was much more pronounced, leading to differences in reversibility. This type of nanostructure provides a sharp control of magnetic hardness that could be tailored in related technologies. [ABSTRACT FROM AUTHOR]

Ni(sub0.82)Fe(sub0.18)O(100) epitaxial films have been grown by solid-source metal-organic chemical vapor deposition. A high exchange field and low coercivity are attributed to the high in-plane anisotropy and the uncompensated spins in the interface. The reduction in blocking temperature may relate to the local Fe-O-Fe or Fe-O-Ni bonding.

We have investigated the effect of microstructure and interface conditions on the anisotropic exchange fields of NiO/NiFe bilayers. The NiO films were deposited by dc magnetron reactive sputtering. By using different substrates or annealing NiO films, grain size and surface roughness of NiO can be manipulated. The exchange field is enhanced in the small-grained NiO and this enhancement is attributed to the formation of small domains in NiO. The degree of interfacial roughness and the existence of (111) texture showed no correlation with exchange field.

Well-aligned (001)-oriented granular or particulate L10 FePt films on amorphous SiO2 or glass substrates were obtained by depositing atomic-scale Fe/Pt/SiO2 multilayers followed by various postannealing conditions. After 350 °C annealing, (001) FePt–SiO2 granular films were obtained with an average grain size of 5.14 nm, perpendicular coercivity of 7.7 kOe, and squareness of 0.95. The diffusion of SiO2 to grain boundaries and free surface of FePt accelerated the diffusion of Fe and Pt atoms to form the L10 phase; therefore, low-temperature ordering of FePt was achieved. By further raising the annealing temperature to 700 °C, isolated particles of aligned (001) single crystals were achieved. The nucleation of voids occurred at low temperatures due to the existence of low-surface-energy SiO2, and then an agglomeration process proceeded, leading to a particulate structure. The isolated particles showed a perpendicular coercivity of 60 kOe and squareness of unity. [ABSTRACT FROM AUTHOR]

Epitaxial {111} Ni[sub 0.82]Fe[sub 0.18]O films (NiFeO) were prepared by using solid-source metal-organic chemical vapor deposition on {0001} α-Al[sub 2]O[sub 3]. The exchange anisotropy between NiFeO and Ni[sub 80]Fe[sub 20] (NiFe) was investigated. Structural and chemical analyses showed that NiFeO films were compositionally homogeneous. The 60-degree rotational twins formed in the NiFeO films. The epitaxial relationship between Ni[sub 0.82]Fe[sub 0.18]O and Al[sub 2]O[sub 3] is the following: [111] NiFeO|[0001]α-Al[sub 2]O[sub 3], [11¯0]NiFeO|[11¯00]α-Al[sub 2]O[sub 3], and [112¯]NiFeO|[112¯0]α-Al[sub 2]O[sub 3]. The orientation relationship between NiFeO and NiFe is cube-to-cube. Misfit dislocations pile up at the interfaces significantly reduce the stress, and result in semi-coherent interfaces. In-plane tension and out-of-plane compression were developed in NiFeO films due to the thermal stress, which may force the magnetic moment of NiFeO to lie in the {111} planes parallel to the film surface, and may lead to a strong interfacial coupling between NiFeO and NiFe. The relative small exchange field possibly results from (1) a low anisotropy energy compared to the interfacial coupling energy in the NiFeO {111} plane, (2) an orientation distribution of the easy axes in the NiFeO {111} plane, and (3) the large domain size of NiFeO. The Malozemoff model was used to estimate the exchange field in this system. Based on the assumption that the domain size of the NiFeO is approximately equal to the twin size, the calculated exchange field agrees well with the experimental results. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

High magnetization (Mr) and enhanced coercivity magneto-optical (MO) recording media TbFeCo (TFC) were investigated for hybrid magnetic flux reading/optical recording due to their large magnetic flux. To increase the stability of high Mr TFC media, dual-layer disks composed of TM-rich readout layer with saturation magnetization (Ms) = 370 emu/[cm.sup.2] and RE-rich memory layer were fabricated. Coercivity and interface energy between double layers as a function of active layer thickness were examined. By simulating thermo-magnetic writing, the dual-layer media were shown to be applicable for optical writing/magnetic flux reading recording. Index Terms--Coercivity, hybrid magnetic flux reading/optical recording, magnetic flux, magnetization.

Textured and epitaxial {001} NiFe/NiMn/Co films were grown on Cu/Si (100) structural templates by using e-beam evaporation. Numerical analysis of high-resolution TEM images was used to determine the local d-spacing of NiMn. The local c/a ratio for the annealed sample varied across the film. The well-aligned orientation relationship between NiFe and NiMn stabilized the disordered NiMn phase, which resulted in a small exchange field. Interdiffusion was observed by energy dispersive X-ray spectroscopy near the interfaces of Cu/NiFe, NiFe/NiMn, and NiMn/Co. Interdiffusion may modify the interfacial structures, and may contribute to the enhancement of the coercivity in NiFe and Co. Index Terms--{001} NiFe/NiMn/Co, exchange field, high-resolution TEM, interdiffusion.