Magnetic exchange interactions and supertransferred hyperfine fields at 119Sn probe atoms in CaCu3Mn4O12

Overview & Synopsis

The double manganite CaCu3Mn4O12 doped with 119Sn atoms (∼1 at.% with respect to manganese atoms) was studied by use of Mössbauer spectroscopy. Formally tetravalent Sn4+ ions substitute for isovalent manganese ions in the octahedral (Mn4+O6) polyhedra. The covalency effects on the magnetic interactions like superexchange in Cu2+-O-Mn4+ and Mn4+-O-Mn4+ bonds and supertransferred hyperfine interactions of the 119Sn probe atoms in the manganite structure are discussed. Using a semiquantitative nearest-neighbor cluster model relating the hyperfine magnetic field on the 119Sn nuclei (HSn = 105 kOe at T = 77 K) to covalency parameters and angle characterizing the Sn-O-M (M = Cu, Mn) bonds, it has been shown how such an analysis of supertransferred hyperfine interactions of tin probe ions can get fruitful information about strength and sign of the superexchange interactions between Mn4+ and Cu2+ magnetic ions. A consistent description of the results in the framework of the Weiss molecular field model considering the specific local environment of tin atoms has made it possible to estimate exchange integrals: JCuMn = −51.1 ± 0.3 K and JMnMn = −0.6 ± 0.2 K.