Long-range Ni/Mn structural order in epitaxial double perovskiteLa2NiMnO6thin films

Abstract

We report and compare the structural, the magnetic, and the optical properties of ordered La 2 NiMnO 6 thin films and its disordered LaNi 0.5 Mn 0.5 O 3 counterpart. An x-ray diffraction ͑XRD͒ study reveals that the B-site Ni/Mn ordering induces additional XRD reflections as the crystal symmetry is transformed from a pseudocubic perovskite unit cell in the disordered phase to a monoclinic form with larger lattice parameters for the ordered phase. Polarized Raman-spectroscopy studies reveal that the ordered samples are characterized by additional phonon excitations that are absent in the disordered phase. The appearance of these additional phonon excitations is interpreted as the clearest signature of Brillouin-zone folding as a result of the long-range Ni/Mn ordering in La 2 NiMnO 6 . Both ordered and disordered materials display a single ferromagnetic-to-paramagnetic transition. The ordered films display also a saturation magnetization close to 4.8 B / f.u. and a transition temperature ͑FM-T c ͒ around 270 K while the disordered ones have only a 3.7 B / f.u. saturation magnetization and a FM-T c around 138 K. The differences in their magnetic behaviors are understood based on the distinct local electronic configurations of their Ni/Mn cations.

Multiferroic double perovskites: Opportunities, issues, and challenges

“…saturation 8 magnetization whereas its value reaches about 3.7µ B /f.u. for the disordered films 14 . The typical temperature dependence of the magnetization (viz., M-T curves) measured in a 500 Oe magnetic field is shown in Figure 3a for the different level of ordering.…”

Electronic and magnetic properties of La2NiMnO6 and La2CoMnO6 with cationic ordering

“…It is different from Mn 3þ /Ni 3þ or Mn 3þ /Co 3þ pairs expected in disorder phase. 8,9,16 According to Goodenough-Kanamori rules, 26 while Mn 3þ -O-Ni 3þ or Mn 3þ -O-Co 3þ has AFM exchange interaction. For the middle valence state, our calculations reveal that Mn (…”

“…[1][2][3][4][5] LNMO thin films have been grown on different substrates, such as NdGaO 3 (110), SrTiO 3 (100), LaAlO 3 (100), and MgO (100). [14][15][16][17][18] Meanwhile, LCMO thin films can be grown on cubic (001) SrTiO 3 substrates by pulsed laser deposition. 19 Either in the form of bulk or films, local Co/Mn or Ni/Mn disorder has been observed which results in the coexistence of multi phases with various behaviors.…”

Phase formation, phonon behavior, and magnetic properties of novel ferromagnetic La3BAlMnO9 (B=Co or Ni) triple perovskites

“…Double perovskite oxides with chemical formula A 2 BMnO 6 (e.g., A = La or Bi, B= Co or Mn) have received considerable interest as magnetoelectric multiferroic materials [1][2][3][4][5][6][7] . These systems show a ferromagnetic insulator 8 behavior and a strong spin-phononpolar coupling [1][2][3][4][5][6][9][10][11][12] .…”

“…These systems show a ferromagnetic insulator 8 behavior and a strong spin-phononpolar coupling [1][2][3][4][5][6][9][10][11][12] . In these systems, ferromagnetism with an insulator characteristic arises due to the 180 o superexchange interaction between B-O-Mn cations, as described by Goodenough and Kanamori 8 .…”