Temperature evolution of 3d- and 4f-electron magnetic ordering in the ferrimagnetic Mn self-doped perovskite (Yb 0.667 Mn 0.333)MnO 3

A high-pressure synthesis method was employed to prepare Mn-self-doped perovskites (R0.667Mn0.333)MnO3 (R = Yb, Lu) at about 6 GPa and 1670 K. Crystal and magnetic structures of (Yb0.667Mn0.333)MnO3 have been studied by combining neutron powder diffraction, magnetic susceptibility and specific heat measurements. Within the orthorhombic space group Pnma, magnetic cations are located on site 4c (A site, occupied by two thirds of Yb3+ and one third of Mn2+) and on site 4b (B site, occupied by two thirds of Mn3+ and one third of Mn4+). The degree of structural distortion of the MnO6 octahedra follows the general trend of (R1-xMnx)MnO3 compounds which shows a decrease with increasing amount of Jahn-Teller inactive Mn4+ cations. Mn - Mn interactions produce a collinear ferrimagnetic structure (TC,Mn = 106 K) with ferromagnetically ordered Mn moments at the B site being coupled antiferromagnetically with ordered Mn moments at the A site. Mn - Yb interactions induce a small but non-zero ferromagnetic Yb3+ moment which can explain a small decrease of the magnetic susceptibility at low temperature. Yb - Yb interactions create an antiferromagnetic structure at TN,Yb = 40 K. Ordered moments of the ferrimagnetic and antiferromagnetic structures are oriented perpendicular to each other within the ac-plane and Yb3+ moments contribute to both structures. The appearance of ordered Yb3+ moments induced by Mn - Yb interactions in perovskite (Yb0.667Mn0.333)MnO3 is a result of the Mn self-doping on the A site and has not been observed in the orthorhombic perovskite modification (space group Pnma) of the undoped parent compound YbMnO3, but interestingly, it also appears in the hexagonal non-perovskite modification (space group P63cm) of YbMnO3.