Twofold spin reorientation and field-induced incomplete phase transition in single-crystal ${\mathrm{Dy}}_{0.5}{\mathrm{Pr}}_{0.5}{\mathrm{FeO}}_3$

We report an intriguing twofold spin reorientation transition of type ${\Gamma }_4\left(G_x,A_y,F_z\right)\to {\Gamma }_1\left(A_x,G_y,C_z\right)\to {\Gamma }_2\left(F_x,C_y,G_z\right)$ for the ${\mathrm{Fe}}^{3+}$ magnetic sublattice near spin reorientation temperatures $T_{\mathrm{SR}1}\sim 77 \mathrm{K}$ and $T_{\mathrm{SR}2}\sim 45 \mathrm{K}$ in a rare-earth orthoferrite ${\mathrm{Dy}}_{0.5}{\mathrm{Pr}}_{0.5}{\mathrm{FeO}}_3$ single crystal. Magnetic-field-induced incomplete spin-configuration transitions (${\Gamma }_4\to {\Gamma }_{41}\to {\Gamma }_{42}$ for $H =20\mathrm{kOe}$ and ${\Gamma }_4\to {\Gamma }_{42}$ for $H =40\mathrm{kOe}$) were observed by measurement of magnetization as a function of temperature. The spin reorientation temperature of a ${\mathrm{Dy}}_{0.5}{\mathrm{Pr}}_{0.5}{\mathrm{FeO}}_3$ single crystal can be controlled by changing the magnitude of the applied magnetic field. We also show that spin reorientation of the ${\Gamma }_1\to {\Gamma }_4$ type between $T_{\mathrm{SR}2}$ and $T_{\mathrm{SR}1}$ can be induced by an applied magnetic field along the $c$ axis. The origin of the intriguing magnetic behavior is ascribed to the anisotropic effective field whose strength is determined by the interactions with $R^{3+}$($R =\mathrm{Dy},\mathrm{Pr}$) spins and can be modified by the external applied magnetic field. It provides deeper insight into the ${\mathrm{Fe}}^{3+}-R^{3+}$ magnetic interaction which dominates the sophisticated magnetic phase transitions in the rare-earth orthoferrites.

Figure 1

Temperature dependence of the magnetization of ${\mathrm{Dy}}_{0.5}{\mathrm{Pr}}_{0.5}{\mathrm{FeO}}_3$ along the $a$ and $c$ axes measured in the external field $H$ = 0.1 kOe. The left inset, zoom in for the magnetization (ZFC and FCC) as a function of temperature along the $a$ axis below 9 K; the right inset, zoom in for the magnetization as a function of temperature along the $c$ axis from 72 to 80 K (for highlighting the SR transition).

Figure 2

Magnetization along the $c$ axis as a function of the temperature measured under different magnetic fields $H$ = 0.1, 20, and 40 kOe.

Figure 3

Hysteresis loops of a ${\mathrm{Dy}}_{0.5}{\mathrm{Pr}}_{0.5}{\mathrm{FeO}}_3$ single crystal along the $c$ axis at temperatures of 45, 50, 60, 65, 70, 75, and 80 K. The field was ramped from 30 to −30 kOe and then to 30 kOe. $H_{crL}$ and $H_{crH}$ correspond to the magnetic fields in between the field-induced SR that occurs from ${\Gamma }_1$ to ${\Gamma }_4$.

Figure 4

Critical fields in the field-induced SR at different temperatures.

Figure 5

Effective field acting on ${\mathrm{Fe}}^{3+}$ spins for the SR of type ${\Gamma }_4\to {\Gamma }_1$, which is projected on the a-b plane for simplicity. (a) Anisotropic effective fields of type ${\Gamma }_4$. (b) Anisotropic effective fields of type ${\Gamma }_1$.