Barkhausen-like magnetization jumps at temperatures T < 9.5 K and the behaviour of the coercive field at low temperatures are studied in sintered Nd-Fe-B magnets with different chemical and phase compositions. The nonlinear temperature dependence of the coercive field H(c) is well described in the thermal activation model at T > 10 K. The low temperature anomalies of H(c) are discussed in terms of the quantum tunneling of the domain wall through the intergrain boundaries.

The magnetoresistance of single crystals of ErGa2, Tb3Co and NdCu2 compounds has been studied in the regions of the field-induced spin-flip transitions. An anomalous increase was found in the electrical resistivity in the intermediate state where the magnetic phases with the different magnetic structures coexist. A theoretical model to explain this anomaly is proposed. The peaks of the electrical resistivity in this model are connected with the s electron reflection from the potential barrier at the interphase boundary separating the phases with different magnetic structures. This effect is the magnetic analogy of so-called Andreev's reflection in superconductors.

The magnetic properties of Er(1-x)U(x)Ga2 intermetallic system single crystals with the hexagonal AlB2 type structure were studied.ErGa2 compound (x = 0) is a collinear antiferromagnet with [0 0 1] as easy axis and its Neel temperature (T(N)) is equal to 7.5 K. UGa2 is a ferromagnet with [1 0 0] as easy magnetisation direction, its Curie temperature is equal to 125 K.It is shown that the orientations of the easy axes of uranium and erbium subsystems are constant for the whole region of concentrations, but each subsystem has its own ordering temperature. Hence, the Er(1-x)U(x)Ga2 system has the orthogonal magnetic arrangement of erbium and uranium subsystems. The magnetic behaviour of an erbium subsystem can be analysed in the RKKY model taking into account only the difference of electronic concentrations for the different compositions. The magnetic behaviour of a uranium subsystem does not contradict the results of the RKKY calculations.

The frequencies of spin excitations in the nuclear subsystem of ferro- and antiferromagnets with a competing uniaxial anisotropy are determined. It is shown that under the conditions of large fluctuations of the anisotropy constant there can exist collective spin modes, corresponding to periodic changes in the variance of the orientational fluctuations of the magnetic moments. The characteristic features of NMR in the system involved in spin-orientational transitions are studied.

Peaks were observed in the longitudinal magnetoresistance in metamagnetic ErGa2 when a two-phase magnetic state existed during spin–flip transitions. The value of the current flowing through a single phase boundary is theoretically predicted to be asymmetric relative to the sign of the potential difference applied across the boundary.