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

Highlights: • (Ho_1−xMn_x)MnO₃ perovskites with x = 0.2 and 0.3 were prepared. • A high-pressure high-temperature method was used. • Magnetic structures were established by neutron powder diffraction. • They show pronounced magnetization reversal effects. • They show magnetic-field-induced first-order transitions. -- Abstract: A high-pressure synthesis method was employed to prepare (Ho_1-xMn_x)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 T_C = 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 (R_1−xMn_x)MnO₃ materials with heavier and smaller rare-earths cations.