Negative magnetization in La0.75Nd0.25CrO3 perovskite

Complex oxides of transition metals (TM) with the perovskite structure have attracted great interest due to a whole series of unique properties such as high-temperature superconductivity, colossal magnetoresistance, coexisting (anti)ferromagnetism, and (anti)ferroelectricity. Recently, several groups have reported negative magnetization observed below a certain temperature on cooling of a sample in a low or a medium (up to 4 kOe) magnetic field. This phenomenon was discovered for LaVO3 [1], YVO3 [2], La1-xGdxMnO3 [3], Nd1-xCaxMnO3 [4], GdCrO3 [5], La1-xPrxCrO3 [6], and some others perovskites. In the present paper, we report on the reversal of the magnetization for LaCrO3–NdCrO3 solids. The end compounds, LaCrO3 and NdCrO3, have an orthorhombic perovskite structure at room temperature (space group Pbnm (Pnma)) [7]. The exchange coupling between the magnetic moments of the Cr ions in LaCrO3 is predominantly antiferromagnetic. G-type of antiferromagnetic structure is established below the Neel temperature of TN = 288 K [6]. The weak ferromagnetic moment, peculiar to LaCrO3, is due to the antisymmetric Dzyaloshinskii–Moriya interaction [8, 9]. In NdCrO3, the magnetic moments of Cr 3+ ions are ordered in GzFx mode (in Pbnm space group notation) at TN = 214 K [10]. Below this temperature, magnetization of the Cr sublattice induces an effective magnetic field on the Nd sublattice due to Nd–Cr interaction leading to a weak ferromagnetic ordering of the Nd magnetic moments in CyFx mode [10]. At TR = 35 K, a Morin-type phase transition occurs and, down to the lowest temperatures, Gy (Cr )–Cz (Nd) antiferromagnetic structure persists [10]. The magnetic moments of rare-earth (RE) ions are polarized due to the coupling with transition-metal subsystem resulting in a noticeable anisotropic contribution to the low-temperature magnetic properties. Dilution of the rare-earth sublattice with diamagnetic ions changes strong anisotropy of RE-TM exchange, thus leading to the intriguing behavior of the magnetization. In this work, we describe magnetic properties of La0.75Nd0.25CrO3 solid solution and discuss possible reasons for the negative magnetization appearance.