Magnetic and electric properties of multiferroic LiFeP2O7. Comparison with LiCrP2O7

The temperature and magnetic field dependence of the magnetic and electric properties of LiFeP 2 O 7 (LFPO) and LiCrP 2 O 7 (LCPO) are studied using a microscopic model and the Green’s function technique. We have shown that LFPO is antiferromagnetic, but shows a weak ferromagnetism along the [Formula: see text] axis which originates from the canted antiferromagnetic order. For LCPO, such a ferromagnetic order along the [Formula: see text] axis is not observed. In the temperature dependence of the electrical polarization [Formula: see text] along the [Formula: see text] axis there is a kink at [Formula: see text] K which is an indirect evidence for the intrinsic magnetoelectric effect in LFPO. Applying an external magnetic field [Formula: see text], the polarization [Formula: see text] increases, stronger for small temperatures and the kink at [Formula: see text] disappears. For LCPO, we do not obtain a kink at [Formula: see text] K. LCPO is polar, but not ferroelectric. We can conclude that the missing magnetoelectric properties in LCPO could be due to the differences in the magnetic orders between LFPO and LCPO.