Thermal and Magnetic Probes of the Monopole Picture in Spin Ice via SQUID Magnetometry

Dysprosium titanate (Dy₂Ti₂O₇) exhibits several low temperature frustrated magnetic states, including a spin ice state at low fields. Single spin-flip excitations above the spin ice configuration manifest as a dilute gas of pairs of oppositely charged Dirac monopole quasiparticles on the pyrochlore lattice. We probe the density, dynamics, and transitional behavior of thermal and magnetic effects of the monopole picture by measuring the non-equilibrium magnetization using a superconducting quantum interference device (SQUID) magnetometer under an applied field and thermal gradient to create a local imbalance of opposite-polarity monopole quasiparticles. We have grown both oriented single crystals and thin films of Dy₂Ti₂O₇ to facilitate this measurement, and to understand the effects of growth conditions and crystal defects on the magnetic landscape of Dy₂Ti₂O₇.