The Jahn-Teller distortion plays an important role in determining the exchange interaction in rare-earth manganites.In this work we study the influence of the Jahn-Teller distortion on the magnetic structures of TbMn1-xFexO3（x = 0,0.02,0.05,0.10,and 0.20） single crystals in the basal MnO2 plane.The decrease in the quadruple splitting with the increasing Fe doping indicates the reduction of the Jahn-Teller distortion,which makes the nearest neighboring（NN） FM interaction dominant over the next nearest neighbor（NNN） AFM interaction.This alteration is favorable for the development of A-type AFM ordering instead of the spiral magnetic ordering,which collapses when x ≥ 0.05.The analysis of dielectric data indicates that the ferroelectricity is arising from the peculiar spiral magnetic ordering.
Magnetocaloric effect （MCE） in polycrystalline HoMn205 was investigated by isothermal magnetization curves from 2 K to 50 K. A relatively large magnetic entropy change, ASM = 7.8 J/（kg·K）, was achieved with the magnetic field up to 70 kOe （10e = 79.5775 A·m-1）. The magnetic entropy change is reversible in the whole range of temperature. The contributions of elastic and magnetoelastic energy to the changing of the magnetic entropy are discussed in terms of the Landau theory. The reversibility of MCE with maximal refrigerant capacity Rc = 216.7 J/kg makes polycrystalline HoMn205 promising as a magnetic refrigerant.
