Field-induced bose-einstein condensation of triplons up to 8K in Sr3Cr2O8

Single crystals of the spin dimer system Sr3Cr2O8 have been grown for the first time. Magnetization, heat capacity, and magnetocaloric effect data up to 65 T reveal magnetic order between applied fields of Hc1∼30.4T and Hc2∼62T. This field-induced order persists up to Tcmax ∼8K at H∼44T, the highest observed in any quantum magnet where Hc2 is experimentally accessible. We fit the temperature-field phase diagram boundary close to Hc1 using the expression Tc=A(H-Hc1)ν. The exponent ν=0.65(2), obtained at temperatures much smaller than Tcmax, is that of the 3D Bose-Einstein condensate (BEC) universality class. This finding strongly suggests that Sr3Cr2O8 is a new realization of a triplon BEC where the universal regimes corresponding to both Hc1 and Hc2 are accessible at He4 temperatures.