Crystal Field Excitations in the defect-fluorite Ho2Hf2O7

Defining single-ion properties is essential to fully understand the physics in rare-earth pyrochlore family of compounds, especially in the vicinity of the ground state. We propose to measure the Crystalline Electric Field (CEF) excitations of Ho2Hf2O7. This compound belongs to the defect-fluorite group (Fm-3m), which exhibits inherent structural disorder. Ho2Ti2O7 is a canonical dipolar spin-ice with a doublet ground state protected by a sizable 200K gap to the first excited state. In contrast to its titanate counterpart, Ho2Hf2O7 remains strongly dynamic down to 0.5K and has a large antiferromagnetic exchange coupling. Magnetic frustration is still present in the defect-fluorite unit cell; therefore, the motivation to this proposal is to explain these changes by obtaining the CEF energy level scheme.