Magnetic instability of d-electron subsystem of RCo2 compounds (R = Dy, Ho) in ultrahigh magnetic fields up to 350 T

Magnetic properties of DyCo2 and HoCo2 have been investigated in both low and high magnetic fields up to 350 T. At low temperature, the compounds form ferrimagnetic structure with the rare-earth moments close to 10 mu(B) and a Co moment of similar to 1 mu(B). With increasing temperature, the magnetic disordering occurs through the first-order type transition, which confirms the itinerant nature of magnetism of d-electron subsystem of Co. From the field dependences of the voltage induced in the measuring coils of the explosive magnetocumulative generator, the values of critical field of metamagnetic transition in the Co sublattice from a field-disordered to a magnetically ordered state were determined to be 295 T and 329 T for HoCo2 and DyCo2, respectively. Using reliable literature data on the field of metamagnetic transition for the exchange-enhanced Pauli paramagnet YCo2, the values of molecular fields of the intersublattice exchange interaction and R-Co exchange coupling parameter were directly estimated. The obtained data are compared with those determined previously by indirect methods.