Nonlinear susceptibilities as a probe to unambiguously distinguish between canonical and cluster spin glasses

作者：Bitla Yugandhar^*; Kaul S N; Fernandez Barquin L

来源：Physical Review B, 2012, 86(9): 094405.

DOI：10.1103/PhysRevB.86.094405

Treating the randomly Fe-substituted optimally hole-doped manganite La0.7Pb0.3(Mn1-yFey)O-3 (y = 0.2,0.3) as a test case, we demonstrate that a combined investigation of both odd and even harmonics of the ac magnetic response permits an unambiguous distinction between the canonical and cluster spin glasses. As expected for a spin glass (SG), the nonlinear ac magnetic susceptibilities chi(3)(T,omega) and chi(5)(T,omega) (odd harmonics) diverge at the SG freezing temperature T-g = 80.00(3) K [T-g = 56.25(5) K] in the static limit and, like the imaginary part of the linear susceptibility, follow dynamic scaling with the critical exponents beta = 0.56(3) [beta = 0.63(3)], gamma = 1.80(5) [gamma = 2.0(1)], and z nu = 10.1(1) [z nu = 8.0(5)] in the sample with composition y = 0.2 (y = 0.3). The nonlinear susceptibility chi(NL), which has contributions from both chi(3) and chi(5), satisfies static scaling with the same choice of T-g, beta, and gamma. Irrespective of the Fe concentration, the values of the critical exponents gamma, nu, and eta are in much better agreement with those theoretically predicted for a three-dimensional (d = 3) Heisenberg chiral SG than for a d = 3 Ising SG. The true thermodynamic nature of the %26quot;zero-field%26quot; spin-glass transition is preserved even in finite magnetic fields. Unlike odd harmonics, even harmonics chi(2)(T,omega) and chi(4)(T,omega) make it evident that, apart from the macroscopic length scale of the spin-glass order in the static limit, there exists a length scale that corresponds to the short-range ferromagnetic order.

• 出版日期2012-9-4