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In sintered (Nd1−xSmxDy)(FeCo)B magnets, the contributions of “soft” (Nd1−xSmxDy)2(FeCo)2B and “hard” (Nd1−xSmxDy)2(FeCo)14B phases to the temperature and field dependences of magnetization have been distinguished. The increase in Sm concentration up to 3% provides stronger interlattice RE-TM (RE—rare-earth metals, TM—transition metals) exchange interaction. Contributions of the NdDy and Sm to magnetic anisotropy have been determined. The competition between the positive contribution of Nd and Dy and the negative contribution of Sm ions results in non-monotonous temperature and Sm concentration dependencies of anisotropy field. Anisotropy of the studied alloys is intermediate between “easy axis” and “easy plane” symmetry.

A spin-reorientation transition accompanied by a decrease in the longitudinal magnetization of α-Fe/PrDyCoFeB microwires was observed at 245 K in zero magnetic field. An increase of the magnetic field at which the microwire is heated from 2 K leads to a significant shift of the transition temperature from 245K at 0 T to 70 K at 1 T. In the perpendicular direction, the change in magnetization at the critical transition temperature is almost absent. Jumps of the magnetic anisotropy and magnetic susceptibility are observed in low fields at a critical temperature. The magnetic phase transition is due to a transition between the ferrimagnetic state of the PrDyCoFeB shell at high temperatures and the state of Ising spin glass at low temperatures.

Microwire of α-Fe(50 at.%)(PrDy)(FeCo)B(48 at.%) was obtained by extracting a hanging melt drop of (PrDy)(FeCo)B in an electron beam. It was shown that a single microwire with a diameter of 50 μm and a length of 0.8 - 6 mm with an amorphous phase (PrDy)(FeCo)B content of ~ 48% and a polycrystalline α-Fe phase of ~ 52% has a rectangular narrow magnetic hysteresis loop and, accordingly, a bistable state with a switching field of ~ 100 Oe. The shortening of the wire to ~ 0.6 mm leads to a sharp deviation from the squareness of the loop, reducing the slope of the dependence of the magnetization on the field and the coercive force to 20 Oe. In the subsurface layers consisting of the amorphous phase (PrDy)(FeCo)B, oriented areas of reverse magnetization are observed. The role of the magnetic dipole interaction in the formation of a magnetic hysteresis loop of chaotic microwire assemblies of various compositions is discussed.

In Gd microwires obtained by ultrafast cooling of the melt, a change in the magnetic entropy of 12 J/kg K was determined at a Curie temperature of 293 K in a magnetic field of 5 T. This value coincides with the change in the magnetic part of the entropy in bulk single-crystal samples in the same field. It has been found that in a strong magnetic field of 9 T, the temperature dependence of the entropy exhibits two maxima at temperatures of 292 and 312 K. The appearance of an additional entropy maximum in microstructured samples is caused by high mechanical microstresses retained in the sample after ultrafast cooling. Keywords: microwires, magnetic entropy, magnetoelastic anisotropy, Curie temperature.