Search

The article provides the analysis of PrDyFeCoB magnetic microstripes prepared by extracting material from a melt on a rotating cooling disk. The phases 2-14-1, 1-4-1 and 1-2, α-FeСо were verified in the samples. The division of a hysteresis loop into two strands shows that the coercive field of the α-FeСо phase (500–700 Oe) determines the width of the hysteresis loop near the zero field, while the coercive field of the 2-14-1 phase (10 kOe) corresponds to lateral hysteresis loops. The saturation magnetization increases by 25% with an increase in the disk rotation speed by 3 times together with correspondent acceleration of the cooling rate. This is due to the increase in the proportion of the soft magnetic phase α-FeCo and the increase in the proportion of the amorphous phase with a decrease in the proportion of the main magnetic phase 2-14-1. Strip domains and their dynamics during magnetization were detected using Kerr magneto-optical microscopy.

The paper gives an analytical review of existing technologies of production and application of micron-sized rare-earth magnets of the RE–TM–B group (microparticles, microwires, films). The specificity of their magnetic properties, which appears at the micron scale, is considered. The analytical comparison of the methods for preparing micromagnets has been carried out. Possible practical applications of micromagnets and their application in various fields of modern technology are systematized. Possible directions of development of micromagnetic technologies are discussed.

International audience

Magnetic anisotropy and interface exchange interaction were analyzed in α-Fe core microwire covered with PrDyCoFeB amorphous shell. The α-Fe/PrDyCoFeB core/shell microwires were grown by pendant drop melt extraction technique providing separation of the α-Fe and PrDyCoFeB phases during the ultrafast cooling. Low saturation field of the core ~100 Oe and high saturation field of amorphous shell ~10 kOe with zero coercivity were distinguished from angular dependences of the magnetic moment, recorded in low and high magnetic fields. Sharp decrease of the longitudinal magnetization, effective anisotropy field and magnetic susceptibility have been observed below the critical temperature, Tcrit = 240 K, in zero field. The Almeida-Thouless transition from ferrimagnetic state to Ising spin glass state has been revealed in PrDyCoFeB amorphous shell. Such spin reorientation transition is very attractive for magnetocaloric applications. We found exchange bias effect controlled by exchange coupling between ferromagnetic core and ferrimagnetic shell. The significance of the obtained data lies in possible applications of the core/shell microwires for tweezers with magnetic moment, stepwise changing in external field. Exchange bias in core-shell interface provides determined initial state of the microwire used as working media of field sensor. The sharp decrease of the magnetization associating with spin-reorientation transition looks very promising for magnetocaloric applications close to room temperature.

Broadening of the 28Si, 29Si isotope distribution in the subsurface layers of Si:B single crystals under plastic deformation has been observed by secondary ion mass spectroscopy. The 28Si, 29Si profiles broaden with increasing dislocation density. Accompanying changes in the 29Si16O profile caused by plastic deformation have been found. The shift of the 29Si16O profile to the crystal bulk correlates well with the 29Si+ isotope redistribution. The uphill diffusion or dislocation movement is a possible driving force of Si and SiO redistribution, whereas selectivity of the isotopes in oxidation reaction is provided by singlet–triplet transitions in Si⋯O short living pairs.