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Classical Spin Nematic Transition in LiGa 0.95 In 0.05 Cr 4 O 8

2017; American Physical Society; Volume: 119; Issue: 8 Linguagem: Inglês

10.1103/physrevlett.119.087201

1092-0145

R. Wawrzyńczak, Yu Tanaka, Makoto Yoshida, Yoshihiko Okamoto, Pascal Manuel, Nicola Casati, Zenji Hiroi, M. Takigawa, Gøran J. Nilsen,

Magnetic and transport properties of perovskites and related materials

We present the results of a combined $^7$Li NMR and diffraction study on LiGa$_{0.95}$In$_{0.05}$Cr$_4$O$_8$, a member of LiGa$_{1-x}$In$_{x}$Cr$_4$O$_8$ "breathing" pyrochlore family. Via specific heat and NMR measurements, we find that the complex sequence of first-order transitions observed for $x=0$ is replaced by a single, apparently second-order transition at $T_f=11$ K. Neutron and X-ray diffraction rule out both structural symmetry lowering and magnetic long-range order as the origin of this transition. Instead, reverse Monte Carlo fitting of the magnetic diffuse scattering indicates that the low temperature phase may be described as a collinear spin nematic state, characterized by a quadrupolar order parameter. This state also shows signs of short range order between collinear spin arrangements on tetrahedra, revealed by mapping the reverse Monte Carlo spin configurations onto a three-state color model describing the manifold of nematic states.