Absence of magnetic long-range order in Y2CrSbO7: Bond-disorder-induced magnetic frustration in a ferromagnetic pyrochlore

作者：Shen L^*; Greaves C; Riyat R; Hansen T C; Blackburn E

来源：PHYSICAL REVIEW B, 2017, 96(9): 094438.

DOI：10.1103/PhysRevB.96.094438

The consequences of random nonmagnetic-ion dilution for the pyrochlore family Y-2(M1-xNx)(2)O-7 (M = magnetic ion, N = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y2CrSbO7 (x = 0.5), in which the magnetic sites (Cr3+) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, (CW)-C-Theta similar or equal to 19.5 K, our high-resolution neutron powder diffraction measurements detect no sign of magnetic long-range order down to 2 K. In order to understand our observations, we construct a lattice model to numerically study the bond disorder introduced by the ionic size mismatch between M and N, which reveals that the bond disorder percolates at x(b) similar or equal to 0.23, explaining the absence of magnetic long-range order. This model could be applied to a series of frustrated magnets with a pyrochlore sublattice, for example, the spinel compound Zn(Cr1-xGax)(2)O-4, wherein a Neel to spin glass phase transition occurs between x = 0.2 and 0.25 [Lee et al., Phys. Rev. B 77, 014405 (2008)]. Our study stresses the non-negligible role of bond disorder on magnetic frustration, even in ferromagnets.

• 出版日期2017-9-28