Magnetic Field Switching between the Two Orbital-Ordered States in ${\mathrm{DyVO}}_3$

The critical phase competition between different spin-orbital-ordered states has been investigated for the ${\mathrm{DyVO}}_3$ single crystal. As temperature is lowered, the compound exhibits a reentrant spin and orbital ordering (SO and OO) transition: $C\to G\to C$ type for SO and $G\to C\to G$ type for OO. It was found that a magnetic field also drives the phase transition from $C$ to $G$ for OO and concomitantly from $G$ to $C$ for SO, the latter of which is coupled with the metamagnetic transition of the Dy $4f$ moments. The mechanism of this novel magnetic-field-induced orbital switching is discussed.

Figure 1

(a),(b) The structures of the $G$-SO and $C$-OO and the $C$-SO and $G$-OO in $R{\mathrm{VO}}_3$, respectively. Open arrows and lobes indicate spins and occupied $d_{yz}$ and $d_{zx}$ orbitals on ${\mathrm{V}}^{3+}$ ions, respectively. (c) Spin-orbital phase diagram of $R{\mathrm{VO}}_3$ ($R=\mathrm{Tb}\mathrm{\text{−}}\mathrm{Er}$), where $r_R$ is the $R$-site ionic radius. Circles, triangles, squares, and double squares indicate $T_{\mathrm{OO}1}$, $T_{\mathrm{SO}1}$, $T_{\mathrm{SO}2}=T_{\mathrm{OO}2}$, and $T_{\mathrm{SO}2}^{*}=T_{\mathrm{OO}2}^{*}$, respectively. (d) The intensity of the (401) Bragg peak shown in Fig. 2a. (e) The $M$ and (f) the integrated Raman scattering intensity of the 63 meV two-orbiton band in $x^{\prime }(zz){\overline{x}}^{\prime }$ polarization (solid circles) and that of the 83 meV phonon band in $z(xx)\overline{z}$ (open circles) shown in Figs. 2b, 2c, for ${\mathrm{DyVO}}_3$. All of the data were measured in a warming run.

Figure 2

(a) Profiles of $\theta -2\theta$ scan for the (401) Bragg peak, which was observed with use of a synchrotron-radiation x ray (9 keV) at BL-4C, Photon Factory of KEK, and Raman scattering spectra for (b) $x^{\prime }(zz){\overline{x}}^{\prime }$ and (c) $z(xx)\overline{z}$ polarizations at various temperatures in ${\mathrm{DyVO}}_3$. The 43 and 63 meV peaks in $x^{\prime }(zz){\overline{x}}^{\prime }$ spectra in the $C$-spin and $G$-orbital phase, indicated by the open triangles, are assigned to the two-orbiton excitation, while those around 83 and 86 meV in $z(xx)\overline{z}$ polarization, indicated by solid and open triangles, to the phonon mode activated in the $C$- and $G$-orbital states, respectively. The transition $T$ ($\sim 22\mathrm{K}$) observed by the measurement of Raman scattering is slightly different from that by the x-ray diffraction, due to the local heating ($<5\mathrm{K}$) on the sample surface by the incident laser.

Figure 3

$T$ dependence of $M$ in $H$ applied parallel to (a) the $a$ axis and to (b) the $b$ axis in ${\mathrm{DyVO}}_3$. All of the measurements were performed in the process of the $H$ cooling and then warming. The inset presents the $M\mathrm{\text{−}}H$ curves for $H\parallel a$, $b$, and $c$ axes at 2 K, respectively.

Figure 4

(a)–(c) show the results for $H\parallel a$ ($x^{\prime }$) and (d)–(f) for $H\parallel b$ ($y^{\prime }$). (a),(d) The $H$ dependence of $M$ was measured after zero-$H$ cooling (ZFC). (b),(e) The spin-orbital phase diagram in the plane of $T$ and $H$. Triangles and circles/squares represent $T_{\mathrm{SO}1}$ and $T_{\mathrm{SO}2}=T_{\mathrm{OO}2}$ ($T_{\mathrm{SO}2}^{*}=T_{\mathrm{OO}2}^{*}$), respectively. The data indicated by circles and squares were obtained by cooling and warming and $H$-increasing and decreasing runs, respectively. Hatched areas indicate the hysteresis region. (c),(f) The Raman scattering spectra indicated as 65 and 10 K ZFC were measured at respective temperatures after ZFC. At 10 K, $H$ is applied along the $a$ or $b$ axis and then removed. After this procedure, the spectra, indicated as 10 K after $H_a=5\mathrm{T}$ or $H_b=2\mathrm{T}$, were measured.