Speaker
Description
Strain in antiferromagnetic orthoferrite thin films is predicted to significantly change magnetic properties and result in a polar response up to room temperature. Orthorhombic DyFeO3 is of particular interest since the Fe-spins undergo a spin-reorientation with transition temperatures depending strongly on the Dy-Fe interaction and a magnetic field induced ferroelectric phase below the Dy ordering temperature of 4K. To gain an understand of the magnetic properties of highly strained, coherently grown (010)-oriented DyFeO3 thin films we studied the pressure dependence of a DyFeO3 single crystal at the thermal triple-axis spectrometer EIGER, SINQ. The scattering experiments were conducted in the (0kl) scattering plane in the temperature range between 1.5 and 100K. For the pressure dependent measurements, a helium gas pressure cell has been used with a max reachable pressure of 5 kbar to study the spin reorientation transition (TSR) at 40K under uniaxial pressure conditions. In the temperature regime of interest, the He-pressure cell has the advantage that the pressure medium is still liquid and the applied pressure therefore truly isostatic. For the single crystal we measure an increase in TSR with a rate of 1K/500bar. As a rule of thumb, a lattice mismatch between film and substrate of 1% corresponds roughly to a chemical pressure of 10kbar. Hence a TSR=70K equals a measured film lattice change of approximately 3%. Overall, pressure depedent magnetic data for a DyFeO3 single crystal are in broad agreement with values obtained for highly strained thin films.
