A.Z. Menshikov

Investigation of the spin-glass state in γ-Fe-Ni-Mn alloys

Abstract The composition region where there are no long-range ferro- and antiferromagnetic order has been determined in γ-Fe-Ni-Mn alloys. In these alloys strong small-angle magnetic neutron scattering has been obtained. The intensity has an unusual temperature dependence which is discussed in the framework of the critical neutron scattering thermodynamic theory. The ground state of these alloys is identified with the spin-glass state in which there are also regions of both short-range ferro- and antiferromagnetic order.

The magnetic state of diamagnetically diluted antiferromagnetic cobalt monoxide

Abstract Magnetic neutron diffraction measurements have been performed on (Co 1− x Mg x )O solid solutions with x = 0.1, 0.2, 0.3, 0.43, 0.53, 0.63 and 0.7 at T = 4.2 –300 K. It is shown that the concentration dependence of the average magnetic moment per atom does not obey the condition of simple dilution. The diamagnetic atom results in a local canting of the moments and an additional reduction of the average magnetic moment. One can consider this atom as a source of random magnetic field due to the appearance of a new superexchange interaction between magnetic atoms through the diamagnetic impurity. The sign of this interaction is opposite to the sign of the direct exchange interaction in the magnetic sublattice.

Magnetic phase transitions in FeGe2

Abstract Magnetic neutron diffraction measurements and a complete symmetry analysis of the FeGe2 magnetic structure is made. At low temperatures a commensurate antiferromagnetic structure with K=(2π/a)(1, 0, 0) exists. At 263 K it tansforms into an incommensurate one through a first-order phase transition. The incommensurate-paramagnetic transition is close to second order due to small anisotropy in the basal plane.

Magnetic structure of Fe(Pd1−xAux)3 and Fe(Pt1−xMnx)3 alloys in the ordered state

Abstract A neutron-diffraction investigation has been performed on the magnetic structures, and their transformations, of the simple cubic magnetic lattice of the ordered Fe(Pd1−xAux)3 alloys as well as the base-centred cubic and tetragonal magnetic lattices of the ordered Fe(Pt1−xMnx)3 alloys. It has been shown, that the transition from the ferromagnetic structure of FePd3 (0, 0, 0) to the antiferromagnetic one of FePd2Au (0, 0, 1 2 ) occurs through the coplanar structure. On the contrary, in the Fe(Pt1−xMnx)3 system the transition region between the collinear structures is characterized by noncoplanar structures in which there is a spin-glass component of the total magnetic moment per magnetic atom in one direction.

MAGNETIC STRUCTURES OF (MN1-XFEX)SN2 INTERMETALLIC COMPOUNDS

Abstract With the aim to understand the nature of the antiferromagnetic phase transition at x ∼ 0.8 in the (Mn1−xFex)Sn2 system, we have performed neutron diffraction measurements for x = 0.2, 0.7, 0.85 and 0.9 between 4.2 and 300 K. The data show that non-collinear magnetic structures exist in the transition region. These may be described by two co-existing wave vectors k 1 = 1 2 1 2 0) and k 2 = (1 0 0) .

Diffuse nuclear and magnetic neutron scattering in quenched alloys

Diffuse neutron scattering measurements were performed on quenched alloys with x = 0.31, 0.36, 0.39, 0.43 and 0.5, which belong to the transition region between ferromagnetism and antiferromagnetism. The nuclear and magnetic cross sections were separated, and Cowley short-range order atomic parameters determined. It was found that the superantiferromagnetic behaviour of these alloys occurred owing to the existence of the antiferromagnetic clusters of the -FeMn type caused by short-range order regions of the CuAu type.