Magnetoelectric coupling tuned by competing anisotropies in Mn${}_{1-x}$Ni${}_x$TiO${}_3$

Abstract

A flop of electric polarization from $P$$\parallel$$c$ ($P_c$) to $P$$\parallel$$a$ ($P_a$) is observed in MnTiO${}_3$ as a spin flop transition is triggered by a $c$-axis magnetic field, $H_{\Vert c}$=7 T. The critical magnetic field $H_{\Vert c}$ for $P_a$ is significantly reduced in Mn${}_{1-x}$Ni${}_x$TiO${}_3$ (x=0.33). $P_a$ and $P_c$ have been observed with both $H_{\Vert c}$ and $H_{\Vert a}$. Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and inter-planar neighbors. In the x=0.33 system, the uniaxial and planar anisotropies of Mn${}^{2+}$ and Ni${}^{2+}$ compete and give rise to a spin reorientation transition at $T_R$. A magnetic field, $H_{\Vert c}$, aligns the spins along $c$ for $T_R$$<$$T$$<$$T_N$. The rotation of the collinear spins away from the $c$-axis for $T$$<$$T_R$ alters the magnetic point symmetry and gives rise to a new ME susceptibility tensor form. Such linear ME response provides satisfactory explanation for the behavior of the field-induced electric polarization in both compositions. As the Ni content increases to x=0.5 and 0.68, the ME effect disappears as a new magnetic phase emerges.

7 pages, 7 figures

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Cited by in corpus (1)

• Correlations and dynamics of spins in an XY-like spin-glass (Ni0.4Mn0.6)TiO3 single crystal system