Measurement of the elastic tensor of a single crystal of and its response to magnetic fields

We have measured the (cubic-lattice-approximation) elastic moduli of optical melt-zone-grown single-crystal (Formula presented) using resonant ultrasound spectroscopy. We observe the structural transition at 285 K to be hysteretic in the ambient (almost zero) magnetic field. A second elastic feature at the ferromagnetic (Formula presented) 265 K, a third at 252 K, and a fourth in magnetic field at 220 K are also observed in this sample, which sits in a particularly complex region in composition space. The application of a magnetic field changes some of the elastic moduli significantly between 220 K and 285 K. By determining the complete elastic tensor, we identify which cubic crystallographic distortions are strongest at each elastic anomaly and which are sensitive to magnetic field. We also determine which bonds play a role in each of the observed features.