Interference of coexisting para- and ferromagnetic phases in partially crystallized films of doped manganites

Abstract

Electron spin resonance spectra have been studied in partially crystallized films of La(1-x)Na(x)MnO(3) (x = 0.16) in the vicinity of the para- to ferromagnetic transition. The objects of investigation were obtained by magnetron sputtering on polycrystalline Al(2)O(3) substrates held at different temperatures. It is shown that, in a regime where the paramagnetic and ferromagnetic phases coexist, the resonance conditions for one phase strongly depend on the parameters of the other phase. As a result, the resonance field of the paramagnetic phase becomes dependent on the shape of the sample, the saturation magnetization and the fraction of the ferromagnetic phase. A simple model is developed to predict the character of the changes in the resonance field of the paramagnetic phase upon the nucleation of the ferromagnetic phase.

Structural first-order transformation in La2/3Ba1/3MnO3: ESR study

“…As a result, in real samples, the transition into magnetically ordered phase is often broadened and characterized by a coexistence of high-temperature (paramagnetic) and lowtemperature magnetically ordered phases over a wide temperature range. The persistence of paramagnetic phase down to the lowest temperatures was experimentally confirmed for various compositions of doped manganites, in particular, for those for which the ground state is ferromagnetic [2,34,41,42,46]. In our case, it is expected that the residual paramagnetic phase is mainly located within the intergrain region.…”

Mixed magnetic state of sodium‐doped manganites and its transformation in the course of para‐ to ferromagnetic transition

“…At T = 290 K, the parameters of the resonance line (resonance field H 0 PM and linewidth DH PM ) are independent of the magnetic field direction. The curves are well fitted by Lorentzians, as is usually observed for the PM state of doped manganites [2,19,20].…”

“…For the parallel case, the resonance field for FM1 line (H ) keeps for the perpendicular case. Such behaviour is characteristic of ferromagnetic regions with in-plane alignment of zero-field magnetization [21], and it has been observed in systems where PM and FM phases coexist [19,20]. The most striking feature of the resonance spectra becomes evident as temperature reaches T 2 % 270 K. At this temperature, a third resonance line (FM2 in Fig.…”

“…2, the resonance field of PM phase shifts to higher values as the fraction of FM1 phase increases. According to calculations and experimental studies [20], this effect reflects the action of the stray fields induced by ferromagnetic phase. Since the fraction of the FM1 phase is greater than that of FM2, the main contribution to these fields originates from the FM1 phase.…”

Influence of miscut direction on magnetic anisotropy of magnetite films grown on vicinal MgO (100)

“…Ferromagnetic resonance ͑FMR͒ measurements were performed at 9.44 GHz on 3 ϫ 3 mm 2 size samples using an ELEXSYS -E500 electron paramagnetic resonance ͑EPR͒ spectrometer equipped with a goniometer and a cryostat to enable angular dependent as well as temperature dependent FMR measurements to be carried out. 16 For both samples studied, we use the following unified coordinate system, which is shown in Fig. 1.…”