Supertransferred hyperfine interaction in magnetic insulators (II)

Abstract

The important mechanisms of supertransferred hyperfine (STHF) interactions in N−O−M chains are briefly discussed: (i) spin polarization ofns states in the N-ion due to the s-d exchange interaction,H ^sd_STHF ; (ii) contributions of spin-polarized states of the intervening O-ion,H ^II_STHF ; (iii) transfer of d-electrons of the M-ion to emptyns states in the N-ion,H ^III_STHF . The dependence ofH _STHF upon the N−O−M bond configuration, electronic structure, and orbital state of the M-ion is presented in a convenient form. The STHF interactions in the chains Sn⁴⁺−O²⁻−Fe³⁺, Cr³⁺ in compounds with slightly distorted Perovskite structure are considered. The STHF field in the chain Sn⁴⁺−O²⁻−Cr³⁺ is shown to change the sign within the range of angles near 170°. This conclusion is in line with published data on the isoelectronic chain Sn⁴⁺−O²−Mn⁴⁺ in the compounds Ca_1−x Sr _x MnO₃. The results obtained for the N−O−Fe³⁺ chain are rationalized by the predicted angular dependence ofH _STHF=α+β cos θ+γ cos²θ. Features of the STHF interactions in N−O−M chains with an M-ion in an orbital degenerate state are examplified by a preliminary analysis of N−O²⁻−V³⁺ chains in orthovanadites.