Electronic and structural transitions in NdFeO3 orthoferrite under high pressures

Abstract

The effect of high pressure up to 65 GPa on the crystal structure and optical absorption spectra of NdFeO3 orthoferrite single crystals is studied in diamond anvil cells. At P∼37.5 GPa, an electronic transition at which the optical absorption edge jumps from ∼2.2 to ∼0.75 eV is observed. The equation of state V(P) is studied on the basis of the X-ray diffraction data obtained under pressure. This study reveals a first-order structural phase transition at P∼37 GPa with a jump of ∼4% in the unit cell volume. It is shown that the phase transition observed in rare-earth orthoferrites at 30–40 GPa is a transition of the insulator-to-semiconductor type.