High-field magnetostriction of spin ices*

In frustrated magnets, geometrical frustration prevents long-range magnetic order and leads to exotic states of matter like spin liquids [1]. Spin ice is such a state whose ground state does not show long-range order, but a short-range “2-in, 2-out” correlation instead [2]. Local Ising anisotropy induced by the competition between crystal electric field (CEF) effect and magnetic interactions are crucial in order to form such spin-ice correlations. Generally, frustrated magnets show characteristic magnetostrictive responses [3] and here, we used magnetostriction as a probe to explore the regime beyond Ising limit in classical spin ice Ho₂Ti₂O₇ and quantum spin ice Pr₂Zr₂O₇ under high magnetic fields up to ~ 50 T. We observed that the longitudinal magnetostriction Δ??/?? of Ho₂Ti₂O₇ under the [111] magnetic field exhibits nonmonotonic change, while that of Pr₂Zr₂O₇ shrinks monotonically. Based on these observations, we discuss the role of CEF effect and exchange-striction effect in driving the behavior of Δ??/??.

Reference:

[1] L. Balents, Nature 464, 199–208 (2010).

[2] S.T. Bramwell, M. J. P Gingras, Science 294, 1495-1501 (2001).

[3] O. Tchernyshyov, R. Moessner, S.L. Sondhi, Phys. Rev. Lett. 88, 067203 (2002).