Features of the magnetic properties of rare-earth intermetallides RMn2Ge2 (Review)

The magnetic and other physical properties of the ternary intermetallic compounds RMn2Ge2 (R is a rare earth) are of great interest on account of effects due to the coexistence of the 3d (manganese) and 4f (rare-earth) magnetic subsystems. The layered structure, the high sensitivity of the exchange parameters to the interatomic distances, the antiferromagnetic exchange interaction in the manganese subsystem in intermetallides containing heavy rare earths, and also the appreciable crystal-field effects in the rare-earth subsystem make for complex magnetic phase diagrams in these compounds. A review is given of the experimental and theoretical research on the magnetic properties and magnetic phase diagrams of the intermetallic compounds RMn2Ge2, including measurements in high and ultrahigh magnetic fields. A theoretical model is proposed which takes into account the features of the crystal structure and the hierarchy of exchange interactions in intermetallides containing heavy rare earths; this model is in many cases capable of describing the magnetic properties of these intermetallides over a wide range of magnetic fields and temperatures, and it permits determination of the interaction parameters for RMn2Ge2 compounds with R=Gd and Dy from a comparison of the experimental and calculated magnetization curves and H–T phase diagrams.