Hydrothermal synthesis and magnetic properties of multiferroic rare-earth orthoferrites

Rare-earth orthoferrites RFeO3 are gifted with fantastic magnetic properties. They have become a research focus for developing multiferroics in recent years. However, it is difficult to obtain pure-phase RFeO3 from the high-temperature synthesis methods. In this work, we report hydrothermal synthesis of well-crystallized pure-phase orthoferrites RFeO3 (R = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in low temperatures. Structures, morphologies and magnetic properties of the products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), magnetic property measurement system (MPMS), vibrating sample magnetometer (VSM), etc. The expected products were determined to be orthorhombic crystals of perovskite structure. The influences of alkalinity, reaction temperature and time on the formation and growth of RFeO3 crystals were investigated in details, and a dissolution-precipitation mechanism was proposed for describing the formation and growth. Optimum hydrothermal conditions for synthesizing orthoferrites RFeO3 were concluded. The magnetic properties were systematically characterized and studied, including antiferromagnetic transition of Fe (TN1), spin reorientation (TSR), compensation effect (Tcomp), ordering of R (TN2), etc. The relation between the magnetic properties of RFeO3 and the ionic radii of R was investigated and discussed. The experimental results in this work may provide fundamental support to the research and development of multiferroic materials.