Spin reorientation transition in dysprosium-samarium orthoferrite single crystals

We report the control of spin reorientation (SR) transition in perovskite $\mathrm{D}{\mathrm{y}}_{1-x}\mathrm{S}{\mathrm{m}}_x\mathrm{Fe}{\mathrm{O}}_3$, a whole family of single crystals grown by an optical floating zone method from $x=0$ to 1 with an interval of 0.1. Powder x-ray diffractions and Rietveld refinements indicate that lattice parameters $a$ and $c$ increase linearly with Sm doping concentration, whereas $b$ keeps a constant. Temperature dependence of the magnetizations under zero-field-cooling (ZFC) and field-cooling (FC) processes are studied in detail. We have found a remarkable linear change of SR transition temperature in Sm-rich samples for $x>0.2$, which covers an extremely wide temperature range including room temperature. The $a$-axis magnetization curves under the FC during cooling (FCC) process bifurcate from and then jump back to that of the ZFC and FC warming process in single crystals when $x=0.5-0.9$, suggesting complicated $4f-3d$ electron interactions among $\mathrm{D}{\mathrm{y}}^{3+}\text{−}\mathrm{S}{\mathrm{m}}^{3+},\mathrm{D}{\mathrm{y}}^{3+}\text{−}\mathrm{F}{\mathrm{e}}^{3+}$, and $\mathrm{S}{\mathrm{m}}^{3+}\text{−}\mathrm{F}{\mathrm{e}}^{3+}$ sublattices of diverse magnetic configurations. The magnetic properties from the doping effect on SR transition temperature in these single crystals might be useful in the material physics and device design applications.

Figure 1

(a) X-ray diffraction patterns of the DSFO single crystal family, the standard diffraction of $\mathrm{SmFe}{\mathrm{O}}_3$ (PDF#74-1474) is plotted in the bottom panel. (b) Zoom-in of (a) for $2\theta$ between 31 and 35 deg, the line is a guide for the eyes as Sm doping is increasing. (c) Lattice parameters of the DSFO family calculated by the Rietveld refinement using the XRD data with different Sm doping concentrations; the parameters $a,b$, and $c$ can be fitted very well by three straight lines.

Figure 2

(a) X-ray Laue photographs for the $a,b$, and $c$ axis are taken at room temperature for the crystal $\mathrm{D}{\mathrm{y}}_{0.4}\mathrm{S}{\mathrm{m}}_{0.6}\mathrm{Fe}{\mathrm{O}}_3$. (b) ZFC magnetizations as a function of temperature for $\mathrm{D}{\mathrm{y}}_{0.4}\mathrm{S}{\mathrm{m}}_{0.6}\mathrm{Fe}{\mathrm{O}}_3$ under an applied magnetic field of 100 Oe in the temperature range from 3 to 350 K. (c) FC magnetizations along the $a$ axis as a function of temperature for $\mathrm{D}{\mathrm{y}}_{1-x}\mathrm{S}{\mathrm{m}}_x\mathrm{Fe}{\mathrm{O}}_3$ under an applied magnetic field of 100 Oe in the temperature range from 3 to 300 K. (d) The FCC and FCW curves of $\mathrm{D}{\mathrm{y}}_{0.4}\mathrm{S}{\mathrm{m}}_{0.6}\mathrm{Fe}{\mathrm{O}}_3$ crystal, with different applied field. Zoom-in FC curves which possess jumping behavior are shown in (e)–(i).

Figure 3

(a) ZFC magnetizations of the DSFO single crystal family as a function of temperature under an applied magnetic field along the $c$ axis, 100 Oe in the temperature range from 3 to 400 K, the inset shows $c$-axis magnetization of $\mathrm{SmFe}{\mathrm{O}}_3$ at $300-750\mathrm{K}$. (b) SR temperatures for the DSFO single crystal family versus Sm concentration, $T_1$ is the temperature when SR begins from low-temperature configuration, while $T_2$ is the ending temperature of SR transition.