Magnetic and magnetotransport properties in Co5Cu95 melt-spun alloys

Giant magnetoresistance (GMR) has been observed in Co₅Cu₉₅ alloys fabricated by melt-spinning. The highest MR change of 28.0% occurs for Co₅Cu₉₅ after annealing at 450°C for 30 min. Based on the super-paramagnetic assumption, the average size of Co particles embedded in Cu matrix, ranging from 3.0 to 6.0 nm, has been determined by simulating the magnetization curves at 295 K which is higher than the blocking temperatures for the samples. Comparison with phenomenological theory for GMR indicates that the interfacial spin-dependent scattering is the dominant scattering mechanism underlying GMR origin in granular systems. Additionally, for the samples in as-quenched state or annealed at temperatureT _A=350°C, the electron hybridization and super-paramagnetic behaviors of fine Co particles may be responsible for the low value of MR change.     

Ground state magnetic properties of ultrathin fcc Fe and Co films on Cu(001) surfaces

The oxidation characteristics of silicon implanted with a low dose of nitrogen (1–3×10¹⁵cm^–2) have been studied for dry oxidation conditions at 1020°C. The wafers were subjected to a pre-oxidation annealing. Complete inhibition of the oxide growth occurs in the initial stage of oxidation, while the oxidation rate for prolonged oxidation is identical to that for pure silicon. The oxidation resistance increases with the implantation dose. The resistance is attributed to the formation of a nitrogen-rich surface film during annealing. This layer, which consists of only a few monolayers, is presumably composed of oxynitride. The electrical characteristics of MOS capacitors formed on implanted wafers show that the interface state density is not significantly increased by the low-dose N implantation.     

Magnetic and electric properties of (Fe,Co)/(Si,Ge) multilayers

We review selected results concerning the interlayer exchange coupling in Fe/Si _x Fe_1−x , Fe/Ge and Co/Si layered structures. Among the ferromagnet/semiconductor systems, Fe/Si structures are the most popular owing to their strong antiferromagnetic interlayer coupling. We show that such interaction depends not only on semiconducting sublayer thickness, but also on deposition techniques and on the chemical composition of the sublayer as well. In similar heterostructures e.g. Fe/Ge, antiferromagnetic coupling was observed only in ion-beam deposited trilayers at low temperatures. In contrast, in Fe/Ge multilayers deposited by sputtering, no such coupling was found. However, when the Ge is partially substituted by Si, antiferromagnetic interlayer coupling appears. For Co/Si multilayers, we observed a very weak exchange coupling and its oscillatory behavior. The growth of Co on Si occurs in an island growth mode. The evolution of magnetic loop shapes can be successfully explained by the interplay between interlayer coupling and anisotropy terms.     

Magnetic properties of the pseudo-binary Fe2(Nb1-xMnx)

The magnetic behavior of the pseudo-binary system Fe₂(Nb_1-xMn_x) is investigated by means of the experimental techniques of X-ray diffraction (XRD), Mössbauer Spectroscopy (MS) and magnetization studies. The XRD results indicate that, up to x=0.3, all samples are single phase with hcp structure. This corresponds to the solubility limit of manganese in this phase. Above x=0.3, all prepared samples present the coexistence of three phases, two with hcp structure and one fcc. The magnetization measurements at low temperatures indicate that the transition temperature increases with the addition of Mn atoms in the Fe₂Nb host (T_N=10 K) up to 58 K for x=0.1. The Mössbauer spectra were fitted with a quadrupole splitting distribution, which indicates that the average quadrupolar splitting increases slightly with the increase of the manganese concentration.     

Pressure dependence of the weak itinerant ferromagnetism of Y(Co1-xAlx)2

Abstract

Y(Co_1-xAl_x)₂ is a weak itinerant ferromagnet for 0.12 < x < 0.20 with a maximum Curie point of about 25 K near x = 0.15. The pressure dependence of the Curie point for samples with 0.14 < x < 0.18 was measured in the temperature and pressure range 5–25 K and 0–8 kbar using a liquid filled lock cell. It was found that T_c was linear in pressure and extrapolated to OK at P_c = 9 ± 1 kbar for all samples. The volume expansion from YCo₂ to x = 0.15 is equivalent to a chemical pressure of -40 kbar so ferromagnetism cannot occur at the lattice constant of YCo₂.     

纳米复合永磁Pr9Fe74Co12B5Snx(x=0,0.5)的磁化行为与磁黏滞性

用熔体快淬法制备了纳米复合永磁样品Pr9Fe74Co12B5与Pr9Fe74Co12B5Sn0.5,分析了样品的起始磁化、反磁化过程,测得样品的总磁化率、可逆磁化率以及样品的磁黏滞性.结果表明,两样品在室温下均表现为单一硬磁相磁化行为,在低温下表现为双相行为,且由于添加Sn后使晶粒均匀化从而导致样品低温下的双相行为更加明显.添加Sn后引起样品中软磁相含量和软磁相晶粒尺寸的增加,使磁化反转中可逆磁化部分增多,且使反磁化形核场降低.磁黏滞性研究表明,热激活体积与软磁相晶粒的大小有关.     

Magnetic properties of (111) Cu/Fe multilayers

The magnetic properties of (111) Cu/Fe multilayers grown on Cu underlayers of several thickness (2000-500-50 Å) on cleaved mica have been investigated by Mössbauer spectroscopy and SQUID magnetometry. The analysis of experimental results suggests that 2.5 monolayers of ψ-Fe interfaced with Cu evolves partially from paramagnetic to ferromagnetic states as the Cu underlayer thickness is reduced to 50 Å and partially from weak to strong antiferromagnetism.     

Surface vs. bulk magnetic properties of Co/Fe(0 0 1) and Fe/Co/Fe(0 0 1) as probed by linear magnetic dichroism in photoemission

The atomic-like behavior of the photoionization cross-section of core levels in solids is remarkably displayed in the observation of linear magnetic dichroism in the angular distribution (LMDAD) of photoelectrons. Nevertheless, structure-related effects are clearly visible as modulations of the dichroism signal, induced by photoelectron diffraction (PED). In this paper a comparison between the PED and LMDAD behaviours is presented for Fe 3p in Fe(0 0 1). In order to separate experimentally the surface and bulk contributions, ultrathin Co/Fe pseudomorphic overlayers were grown on the Fe(0 0 1) surface. Results confirms the PED nature of LMDAD modulations, which can be used as an estimate of the bulk sensitivity of the experiment.     

Magnetic and magneto-optical properties of CoFeCrSiB amorphous ribbons

In this paper we investigate the surface magnetic properties of as-quenched (AQ) CoFeCrBSi ribbons prepared by planar flow casting method with using magneto-optic Kerr effect (MOKE). Measured hysteresis loops in longitudinal and transversal configurations enable us to obtain the information of ribbons surface magnetic properties. Moreover, we suggest new magneto-optic method, which is based on measurements of magneto-optical effects depending on DC current flowing through the ribbon. Experimental data of AQ ribbons are then compared with the model, which describes the influence of incidence angle on magneto-optical angles.     

Magnetic properties of submicron size particles made from Fe/Co multilayers

Arrays of submicron size (0.15 μm) particles of 23 and 35 nm thick Fe(2 ML)/Co(6 ML) multilayers were investigated by magnetization measurements and magnetic force microscopy. The behaviour of elliptical particles is mainly determined by their shape anisotropy. Varying the lateral size and thickness of the particles there is a transition from multi-domain to single-domain states.     

Magnetic properties of Co clusters deposited on Pt(111)

Using the fully relativistic version of the Korringa–Kohn–Rostoker method for electronic structure calculations within local spin density functional theory, the magnetic and spectroscopic properties of Co clusters deposited on Pt(111) have been investigated. Of central interest was the role of spin–orbit coupling, since it influences the spontaneous formation and orientation of magnetic moments and gives rise among other things to the occurrence of orbital magnetic moments, magnetic anisotropy energy and magnetic circular dichroism in X-ray absorption. The results have been complemented by calculations of the exchange coupling parameters J_ij used within Monte Carlo simulations on the basis of the extended classical Heisenberg Hamiltonian. This allowed us to simulate the magnetic properties at finite temperatures, which are of central importance for applications. PACS 73.20.-r; 71.15.Rf; 73.22.-f; 87.64.Ni     

Magnetic properties of ultrathin Co films on Si (111)

Ultrathin cobalt films on clean (7×7) and Au covered Si (111) substrates were prepared by molecular beam epitaxy. The structure was studied by using scanning tunnelling microscopy and low energy electron diffraction. Magnetic properties were determined with the magneto-optic Kerr effect. It was found that Co nucleates in grains that prefer to grow along the bunched step edges of the Si substrate ([112?] direction), which induces a strong in-plane uniaxial anisotropy. By introducing Au buffer layers, the magnetic characteristics were improved by preventing the silicide reaction between Si and Co. Moreover, the tendency for step decoration disappears gradually results in the in-plane uniaxial anisotropy reduction.     

Magnetic properties of 57Fe/Ir(100) superlattices

Summary The synthesis of a new BCT Fe phase was performed in Fe/Ir(100) superlattices grown by MBE. Magnetic properties of⁵⁷Fe/Ir(100) superlattices with 4 ml Fe and variable Ir thickness (2–30 ?) are investigated by⁵⁷Fe conversion electron M?ssbauer spectroscopy in the 4.2–300 K temperature range. Two spectral components are evidence, related, respectively, to Fe atoms involved in the central part of the iron layers and at the interface between iron and iridium layers. The appearance of a high magnetic hyperfine splitting in the iron BCT structure above a volume threshold of 12 ?³ is evidenced. Marked differences are observed between the mean magnetic properties and the local ones suggesting strong relaxation effects. Paper presented at ICAME-95, Rimini, 10–16 September 1995.     

Magnetic anisotropy of amorphous (Fe1−x Co x )78Si10B12 alloys

In order to better understand the problem of magnetic anisotropy in amorphous alloys produced by a rapidly quenching technique, in-plane magnetic anisotropy of amorphous (Fe_1−x Co _x (₇₈Si₁₀B₁₂ alloys was measured by means of a torque magnetometer using a disk specimen made from the amorphous alloy ribbon. The amorphous ribbons were prepared by a single roller type quenching apparatus. It was found that the anisotropy had mostly twofold symmetry in all the alloy cases, and that the concentrationx dependence of the anisotropy constant behaved differently from that of the magnetostriction. Moreover, the anisotropy did not disappear by subsequent annealing at high temperatures where the internal stress relief and the crystallization were completed.