Magnetic properties and ferrimagnetic structures of Mn self-doped perovskite solid solutions (Ho1−xMnx)MnO3

A high-pressure synthesis method was employed to prepare (Ho1-xMnx)MnO3 solid solutions with x = 0.2 and 0.3 (at about 6 GPa and 1,670 K) and magnetic properties and structures were investigated by magnetic, dielectric and neutron diffraction measurements. Both samples crystallize in the GdFeO3-type Pnma perovskite structure, and both samples show magnetization reversal behavior below the compensation temperature of about 35 K (at H = 100 Oe). The magnetization reversal phenomena are originated from a ferrimagnetic (FiM) structure which takes place below TC = 76 K (x = 0.2) and 102 K (x = 0.3) and is built from ferromagnetic (FM) ordering of Mn3+ and Mn4+ cations at the B site which are antiferromagnetically (AFM) coupled with Ho3+ and Mn2+ cations at the A site. The magnetic moment of Ho3+ cations increases significantly with deceasing temperature, and it overcomes the saturated magnetic moment of Mn3+ and Mn4+ cations at the B site. Field-induced first-order transitions were found in both compounds below about 35 K. Neutron diffraction measurements on the x = 0.2 sample found a collinear FiM structure between 76 K and 40 K, and the development of spin canting at the A site below 40 K. The coexistence of Ho3+ and Mn2+ at the A-site gives rise to additional short-range magnetic ordering of Ho3+ and to strain effects along the a-direction which are stronger than in (R1−xMnx)MnO3 materials with heavier and smaller rare-earths cations.