Magnetoelastic effects in the trigonal 4f-3d crystals: RFe3(BO3)4

Low-temperature magnetoelastic effects in the rare-earth (RE) ferroborates RFe3(BO3)4 with various REs are theoretically investigated. The RE magnetoelastic Hamiltonian is written in the multipole approximation and the field and temperature dependences of the multipole moments and strain susceptibilities are calculated for the RE ions in the ferroborate structure. Contributions of the iron and RE subsystems to magnetostriction are analyzed. Magnetoelastic anomalies caused by the magnetic-field-induced phase transitions are discussed and possible anomalies of elastic constants are predicted. The expressions obtained for magnetoelastic effects are valid for any RE crystal of trigonal symmetry