Magnetic anisotropy and magnetic phase transitions inRFe10Mo2(R=Pr, Nd, Sm, Dy, Ho, Er, Tm)

Abstract

${\mathrm{RFe}}_{10}$ ${\mathrm{Mo}}_{2}$ (R=Pr, Sm, Nd, Dy, Ho, Er, Tm) intermetallics were investigated by studying the temperature- or field-induced spin-reorientation transitions (SRT's). The temperature dependence of the magnetic anisotropy field was determined by means of the singular point-detection technique for the polycrystalline samples of ${\mathrm{YFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , ${\mathrm{NdFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , ${\mathrm{DyFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , and ${\mathrm{ErFe}}_{10}$ ${\mathrm{Mo}}_{2}$ . Main emphasis was given to the theoretical analysis of the magnetic anisotropy constants and the magnetic phase transitions. The temperature dependences of the rare-earth anisotropy constants were calculated using the single-ion model within linear theory. The applicability of the linear theory of the R anisotropy is discussed. It is shown that the accuracy of this theory increases considerably with increasing temperature. Fitting the experimental data, a set of the crystal field and exchange field parameters for the rare-earth ${\mathrm{R}}^{3+}$ ions was deduced. The observed SRT's and first-order magnetization processes (FOMP's) were explained and classified. FOMP-like transitions in ${\mathrm{PrFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , ${\mathrm{HoFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , and ${\mathrm{ErFe}}_{10}$ ${\mathrm{Mo}}_{2}$ were identified. The temperature dependence of the FOMP fields was calculated for ${\mathrm{HoFe}}_{10}$ ${\mathrm{Mo}}_{2}$ and ${\mathrm{ErFe}}_{10}$ ${\mathrm{Mo}}_{2}$ . The physical origin of a low-temperature anomaly in the magnetization process is discussed for ${\mathrm{SmFe}}_{10}$ ${\mathrm{Mo}}_{2}$ . The spin-reorientation transitions in ${\mathrm{ErFe}}_{10}$ ${\mathrm{Mo}}_{2}$ and ${\mathrm{TmFe}}_{10}$ ${\mathrm{Mo}}_{2}$ are determined to be of first order with a discontinuous jump of the magnetization. The SRT's detected in ${\mathrm{NdFe}}_{10}$ ${\mathrm{Mo}}_{2}$ and ${\mathrm{DyFe}}_{10}$ ${\mathrm{Mo}}_{2}$ are of second order. The calculated temperature dependences of the anisotropy fields for ${\mathrm{DyFe}}_{10}$ ${\mathrm{Mo}}_{2}$ and ${\mathrm{NdFe}}_{10}$ ${\mathrm{Mo}}_{2}$ are in good agreement with the experimental data over a wide temperature range. FOMP's are predicted at low temperatures for ${\mathrm{NdFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , ${\mathrm{DyFe}}_{10}$ ${\mathrm{Mo}}_{2}$ , and ${\mathrm{TmFe}}_{10}$ ${\mathrm{Mo}}_{2}$ .