P. Granberg

Non-equilibrium relaxation in a Cu(Mn) spin glass

The zero-field dynamics of a Cu(10 at% Mn) spin glass system has been investigated by means of zero-field-cooled magnetization measurements. By subjecting the sample to specific temperature variations just before the field application, new information about the nature of the spin glass phase is obtained. The results are in accord with some predictions from domain theories on the behaviour of the magnetic relaxation in spin glasses. Specifically, the experimental results support the prediction that the spin glass dynamics is governed by an interplay between a growing domain size and the overlap length.

Structural and magnetic properties of (Fe1-xCox)3P compounds : experiment and theory

Abstract The structural and magnetic properties of (Fe1−xCox)3P compounds have been investigated by means of X-ray and neutron diffraction experiments, magnetization measurements and first-principles calculations. The saturation magnetization and the transition temperature of (Fe1−xCox)3P decrease with increasing Co concentration. The magnetic moments on the three non-equivalent metal sites are determined in detail by means of neutron diffraction experiments and first principles calculations which both show that the moments on the different sites have different magnitudes and they all decrease with increasing Co concentration. Results show that Co preferentially substitutes Fe on two of the metal sites. The complex behavior of the individual magnetic moments and the site preferences of Co substitution are discussed in terms of atomic radius, coordination numbers, and eigenvalue sums.

Experimental evidence for the existence of an overlap length in spin glasses

Zero‐field‐cooled magnetization measurements on a Cu(10 at.% Mn) spin glass are reported. The relaxation of the magnetization is recorded after specific temperature variations of the sample in the spin‐glass phase. The data are discussed within the framework of new domain theories of the spin‐glass phase. A qualitative agreement between the theoretical predictions and the experimental results is found. Specifically, empirical support for the theoretical concept overlap length is given.

Magnetocrystalline anisotropy of (Fe1−xCox)3P

The magnetocrystalline anisotropy energy (MAE) of (Fe1−xCox)3P (x=0, 0.1, 0.2, 0.33) has been studied in the temperature range 5 K–300 K. The compound crystallizes in a tetragonal structure with three non-equivalent metal sites and shows an easy planar behavior with the magnetic moments aligned in the ab plane and the c axis as the hard direction. The MAE of Fe3P was investigated using magnetization measurements on a single crystalline sample. The anisotropy constants were found to be K1≈−851 kJ/m3 and K2≈9 kJ/m3 at 5 K and K1≈−648 kJ/m3 and K2≈11 kJ/m3 at 300 K. The MAE of the cobalt substituted systems was investigated on sintered samples formed into spheres. K1 for these samples was calculated from a fit of the magnetization versus internal field strength using the law of approach to saturation.

Aging in a two-dimensional CuMn spin glass

Utilizing zero-field cooled magnetization measurements the nonequilibrium dynamics in a 2D spin glass film is investigated. The experiments show that aging is an inherent property of 2D spin glass systems with qualitatively similar features as in 3D systems.

Magnetic properties of NdFeB magnets prepared by extrusion and sintering techniques

Abstract NdFeB permanent magnets have been manufactured by extrusion of gas atomized powder of the nominal composition Nd 16 Fe 78 B 6 . The magnetic properties are found to be anisotropic. The energy product, intrinsic coercive field strength and the remanent flux density measured perpendicular to the extrusion direction are 90 kJ/m 3 , 880 kA/m and 0.72 T respectively.

Nonlinear susceptibility of 2D spin glass films

Abstract A careful study of the nonlinear susceptibility of multilayered two-dimensional Cu(14 at% Mn) spin glass layers separated by thick interlayers of Cu is reported. The experiments were performed in SQUID magnetometers using an ac susceptibility technique in the field range 0–0.5 kG and dc magnetization measurements in the field range 0–10 kG. The static 2D critical exponents have been determined from scaling analysis.

MULTILAYERED SPIN-GLASS FILMS - SENSITIVE PROBES OF RKKY

A new method that uses superstructures of Cu(Mn) spin glass films separated by metallic interlayers to probe the decay with thickness of the RKKY interaction within the interlayers is discussed.

Magnetism in spin glasses

Abstract Experimental results on the relaxation of the magnetization of spin glasses at temperatures below the spin glass freezing temperature T g show very similar behaviour for different spin glass materials. Some data on relaxation are presented and discussed in the context of a droplet scaling theory for the spin glass phase elaborated by Fisher and Huse (Phys. Rev. B, in print).