Influence of K addition on the magnetic and magnetocaloric properties of La2-xKxNiMnO6 (x = 0, 0.2 and 0.4) double perovskite

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

“…Moreover, the Ms and coercivity of the Dy 2 Ni 0.6 Al 0.4 MnO 6 and Dy 2 Ni 0.4 Al 0.6 MnO 6 samples show an apparent increase with temperature decrease, which is different from that of the Dy 2 NiMnO 6 samples. These results again indicate that, besides the Ni 2+ –O–Mn 4+ FM interaction, Mn 3+ –O–Ni 3+ FM interaction appears in the Al 3+ doped Dy 2 Ni 1– x Al x MnO 6 (0.2 ≤ x ≤ 0.6) samples . For the Dy 2 Ni 0.2 Al 0.8 MnO 6 sample (Figure e and S6e, Supporting Information), the temperature of the M‐H hysteresis loops appearance is low to 20 K, and the Ms and coercivity increase only at 4 K, which indicates that the Mn 4+ –O–Ni 2+ FM interactions weaken and the new FM interaction (the Mn 3+ –O–Ni 3+ FM interactions) becomes dominated.…”

“…Concerning the observed T C2 at around 40–55 K for x ≤ 0.6 (for x ≥ 0.8, no transition temperatures of T C2 can be observed), however, the impact of the possible spin‐glass state and the related natural expected ground state to the possible mixing of Ni 2+ –O–Mn 4+ , Ni 2+ –O–Mn 3+ , Mn 3+ –O–Mn 4+ , Ni 3+ –O–Mn 3+ , Ni 3+ –O–Mn 4+ etc, can be ruled out, since no frequency‐dependent cusp and shift can be found in the real part of the AC susceptibility curves at 35–55 K (see Figure S4, Supporting Information), suggesting the unchanged B‐site order (Ni(Al)/Mn arrangement order) structure even with Al doping. From the above‐mentioned XRD, XPS, and Raman results, it can be suggested that the observed T C2 at around 40–55 K originates from the Mn 3+ –O–Ni 3+ FM interactions, which is closely related to the above‐mentioned resonance effect of ionic valences. The observed T N at around 20–40 K originates from the anti‐parallel alignment of rare earth moment with respect to the Ni(Al)/Mn moments.…”