Resonance Effect of Ionic Valences on the Structural and Magnetic Properties of Dy2NiMnO6 Induced by Nonmagnetic Al Ion Doping

• Published in: physica status solidi (b) 2019-10, Vol.256 (10), p.n/a
• Main Authors: Wu, Liang, Shi, Lei, Miao, Xianbing, Zhou, Shiming, Zhao, Jiyin, Pan, Shiyou, Guo, Jianhui, Yuan, Xueyou
• Format: Article
• Language: English
• Subjects: band gap; double perovskites; Dy2Ni1–xAlxMnO6; magnetic phase transitions; super‐exchange interactions
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201900168

Magnetic and structural properties of nonmagnetic Al3+ doping in Dy2NiMnO6 compounds have been investigated systematically. The X‐ray diffraction shows that all the samples are crystallized in double perovskite. The UV–vis absorption spectra present a non‐monotonous dependence of optical band gap on the Al3+ doping content, which is attributed to the local structural distortion induced by Al3+ doping. Magnetization curves show three magnetic transitions corresponding to the temperatures TC1, TC2, and TN, which are attributed to ferromagnetic interactions of Mn4+–O–Ni2+, Mn3+–O–Ni3+, and antiferromagnetic interactions of the Dy3+ with the Ni(Al)/Mn moments, respectively, changing with the Al3+ doping content. A resonance effect of ionic valences has been observed while Al3+ doping at Ni site (B site), i.e., not only the Mn valence decreasing, but also the Ni valence increasing, without destroying the long‐range Ni–O–Mn orders. The Al3+ doping causes the weakening of the super‐exchange interaction between Mn4+ and Ni2+ ions and the Ni/Mn ordered degrees. Meanwhile, the amount of Mn3+ and Ni3+ ions and the strengthening of the Mn3+–O–Ni3+ ferromagnetic interactions increase with trivalent Al ion doping. As a result, TC1 decreases, TC2 and TN increase first and then decrease, showing a non‐linear change, with the Al3+ doping content increase. The resonance effect of ionic valences provides a new way to understand and adjust the magnetic properties for the application. Resonance effect of ionic valences results in the amount increase of Mn3+ and Ni3+ ions without destroying the long‐range Ni–O–Mn orders. Meanwhile, the Mn3+–O–Ni3+ ferromagnetic interactions are enhanced in Al‐doped Dy2NiMnO6 compounds, showing a nonlinear change, similar to that of the antiferromagnetic interactions between Dy3+ ions and Ni(Al)/Mn moments, with Al doping, although the Mn4+–O–Ni2+ ferromagnetic interactions decrease.