Enhanced magnetic properties of La2MgxNi1-xMnO6 bulks prepared at a low temperature

Substitutional effect of Mg2+ on structural and magnetic properties of La2MgxNi1‐xMnO6 double‐perovskite thin films

“…The temperature‐dependent field cooling magnetization of the LM x NMO thin films is measured at 1000 Oe, and the derivative of magnetization to temperature (dM/dT) corresponding to the ferromagnetic‐paramagnetic transition point ( T C ) is further calculated, as depicted in Figure 7. It is found that all the films have only one obvious T C point, different from the LM x NMO ceramics which usually possess two T C points 31 . Therefore, the Ni 2+ ‐O‐Mn 4+ super‐exchange ferromagnetic interaction plays a dominant role in the epitaxially grown LM x NMO thin films 34,53,54 .…”

“…[28][29][30] Consequently, employing different ions to substitute at Bsites can be regarded as an efficient manoeuvre to further improve the magnetic properties of LNMO. Our previous study 31 has verified that Mg 2+ is an effective substitutional ion for the Ni site, which has optimized the crystal structure and enhanced the magnetic properties in LNMO ceramics significantly. However, the substitutional effect of Mg 2+ in LNMO thin films has not yet been reported.…”

“…The LM x NMO thin films with different Mg-doping concentrations (x = 0, 0.1, 0.2, 0.3, 0.4, respectively) were grown on (00l)-oriented LaAlO 3 (LAO) wafers by pulsed laser deposition (PLD, PLVD-362, Electronics Optics Research, Ltd., Japan) since it is a universally recognized method that is very useful to preserve the stoichiometry of the target well in the deposited film even for multicomponent compositions. 32,33 Dense LM x NMO (x = 0, 0.1, 0.2, 0.3, 0.4) bulks for the targets of film deposition were prepared by ultra-high pressure sintering, 31,34 which possessed the advantages to form stoichiometric compositions. A KrF excimer laser, operating at 248 nm wavelength with a repetition rate of 5 Hz and a pulse duration of 20 ns, was employed to ablate the targets.…”

“…Figure 5(a) shows the Raman spectra of the LM x NMO thin films, where the information about the vibration of Ni-O-Mn octahedron and the ordering/disordering degree at B-sites can be exposed. 21,31,[45][46][47][48][49] There are two distinct spectral peaks in the range of 400-800 cm −1 : the peak located at ∼520 cm −1 corresponds to the asymmetric stretching vibration (ASV) mode of Ni 3+ -O-Mn 3+ octahedron while the peak situated at ∼640 cm −1 represents the symmetric stretching vibration (SSV) mode of Ni 2+ -O-Mn 4+ octahedron. It is obvious that the intensity of SSV mode is significantly higher than that of ASV mode, which implies that the B-site ordering plays a dominant role in the LM x NMO thin films.…”

“…It is found that all the films have only one obvious T C point, different from the LM x NMO ceramics which usually possess two T C points. 31 Therefore, the Ni 2+ -O-Mn 4+ super-exchange ferromagnetic interaction plays a dominant role in the epitaxially grown LM x NMO thin films. 34,53,54 With the increasing of Mg-doping concentration, the Curie temperature of the films shows a decreasing trend, since a plethora of Mg 2+ will gradually turn to replace Ni 2+ occupation instead of Ni 3+ position, which should reduce the intensity of the super-exchange ferromagnetic interaction of Ni 2+ -O-Mn 4+ structure.…”