Evidence of a Griffiths phase in a mixed compound of YFe2 and YFe3

Abstract

Experimental evidence of a Griffiths phase is still a challenging topic in condensed matter physics. We show that a mixed compound of YFe2 and YFe3 is an archetype example of Griffiths-like behavior. We report magnetization measurements carried out on the intermetallic mixed compound of YFe2 and YFe3 in the temperature range of 10-1000 K and using magnetic fields up to 23 T. The low-field dc magnetic susceptibility (χ = M/H) showed a thermomagnetic irreversibility effect below the Curie temperatures, TC = 526 K for YFe3 and TC = 545 K for YFe2. Specifically, we found that upon field-cooling (FC), the magnetization increased gradually with decreasing temperature and then reached a saturation value at a critical temperature. In contrast, the zero-FC measurements showed a much more complicated behavior. This behavior has been interpreted in terms of two canted sublattices coupled ferromagnetically. Furthermore, for temperatures above TC, the inverse susceptibility, χ−1, shows a clear downturn, exhibiting non-universal behavior for magnetic fields up to 1 T. This anomaly is characteristic of non-universal Griffiths like behavior. Using the equation for the magnetic susceptibility for the Griffiths phase, χ−1=C(T-TCM)1−λ, we obtained the non-universal prefactor exponent, λ, and the other fitting parameter for each measuring field. The isothermal magnetization curve at Curie temperature, TC = 545 K obeys perfectly M ∼ Hα, from which the critical exponent α = 1/δ is determined accurately. All these results closely follow the predictions for Griffiths phase. In our scenerio, the YFe3 regions (TC = 526 K) distributed homogeneously in the matrix are quenched by the demagnetizing fields of YFe2 (TC = 545 K) as the temperature increases, leading to ordered Fe regions, which in turn cause the Griffiths effect.