Field dependence of spin glass transition temperature in Cu:Mn single crystals

The nature of the spin glass transition in the presence of a magnetic field is a subject of longstanding controversies. Prior studies [Phys. Rev. Lett. 66, 2923 (1991)] used polycrystalline Cu:Mn samples to explore magnetic field dependence of the spin glass transition temperature. They reported the presence of a single d’Almeida-Thouless (AT) transition temperature in low magnetic fields and the presence of two transition temperatures in high magnetic fields which are interpreted as the AT and Gabay-Toulouse (GT) transitions. However, a distribution of crystal sizes introduces multiple coherence length scales with a distribution of glass transition temperatures [Phys. Rev. B 91, 014434 (2015)] which introduces additional complexities in interpreting these results simply as the AT and GT transitions. Here we report preliminary results of magnetic field dependence of spin glass transition temperature for large single crystal Cu:Mn samples with different Mn concentrations. Our preliminary results show that in low fields, the temperature of the onset of irreversibility (M_FC - M_ZFC) decreases with increasing magnetic field strength, but the cusp of the temperature-dependent M_ZFC curve does not.