Low energy THz excitations in distorted perovskites under strong magnetic fields and low temperature.

We report on the magnetic field evolution of distinctive absorption bands in several zero field cooled polycrystalline RMO$_{\mathrm{3}}$ (R$=$ Pr, Nd, Sm, Er, Tm, Lu; M$=$ Cr, Mn, Fe. Ni) at low temperatures. Measurements below 120 cm$^{\mathrm{-1}}$ were done in an 11 T magnet combined with a Bruker IFS125-HR interferometer at the THz beamline of the BESSY II storage ring. At the reordering spin temperature, the spectra of ErCrO$_{\mathrm{3}}$ show an Er-Kramers doublet at \textasciitilde 55 cm$^{\mathrm{-1}}$ following a second order continuous reorientation. It suggests strong anisotropic Er$^{\mathrm{3+}}$-Cr$^{\mathrm{3+\thinspace }}$magnetic exchange interactions. The band strength of its triplet excited states decreases upon increasing the magnetic field. Non-Kramers Pr in PrCrO$_{\mathrm{3}}$ implies a magnetic field induced quasi-doublet system. Spin wave modes AF and F are also tentatively assigned. In ErFeO$_{\mathrm{3}}$, the spin reordering of the canted transition metal, and the Er$^{\mathrm{3+}}$ exchange, is monitored emerging above 80 K. Temperature dependent multiplet transitions centered at 50 cm$^{\mathrm{-1}}$ and 110 cm$^{\mathrm{-1}}$ appear as asymmetric field dependent broad lines. The absence of activity at \textasciitilde 4 K in SmCrO$_{\mathrm{3}}$, shared by SmMO$_{\mathrm{3\thinspace }}$(M$=$Fe, Ni), is consequence of near Cr-canted-Rare-Earth-opposite moment compensation juxtaposed to random micrograin orientation. We will also comment on observed only in ErNiO$_{\mathrm{3}}$ field dependent Er transitions and band profiles.