We studied magnetic properties of thin Ge:Mn films obtained by implantation of Mn + ions into a single crystalline bulk germanium. In the net magnetic moment we were able to separate contributions originating from dispersed Mn 2+ ions, ferromagnetic Mn 5 Ge 3 precipitates, and regions of the germanium matrix enriched with diluted manganese-Mn m Ge n alloys. In the subsystem of dispersed Mn 2+ ions we observed a percolation transition into the ferromagnetic state at T Յ 13 K. Collective excitations, standing spin waves, were also detected below this temperature. The main parameters of the exchange interaction obtained from the analysis of the experimental spin-wave resonance data are consistent with results acquired from static magnetic measurements as well as with theoretical estimations for a percolation ferromagnet. Thus, we demonstrate that low-temperature magnetic properties of group IV magnetic semiconductor can be successfully explained within a magnetic polaron model.

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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.

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