Torque Magnetometry and Thermomagnetic Capacity Studies on a 2-d Cr$^{4+}$ Antiferromagnet

We report torque magnetometry and magnetic heat capacity measurements on a rare complex, Cr$^{IV}$-Diethylenetriamine diperoxo. The motivation here was to search for a simple spin-gap system that could exhibit a Bose-Einstein type condensation (BEC) of magnons. Our earlier reported magnetization and specific heat ($C_{p})$ measurements had indicated that this compound is a 2-d antiferromagnet, with a $T_{N}$ of 2.55 K in zero-field [1]. These magnetization and $C_{p}$ data have now been augmented by use of additional magnetic fields, and the newly found B-$T$ phase diagram is seen to be clearly parabolic. Torque magnetometry confirmed the $C_{p}$ data and has enabled measurements close to the $T \quad \to $ 0 K, B $\sim $ 12.5 T region. Measurements in the dilution fridge are planned to extract the critical exponent ($\alpha )$ from the relation $k_{b}T_{c} \quad \sim $ (B$_{c}$-B)$^{\alpha }$ . We surmise that this system will constitute a simple new model for examining the BEC of magnons in detail. [1] C.M. Ramsey, B. Cage, P. Nguyen, K.A. Abboud, N.S. Dalal, Chem. Mater. \textbf{15}, 92 (2003).