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In this paper, LaFe0.75Cr0.25O3 was synthesized by a citric acid combusting sol–gel method. The basic structural information is reflected by XRD. According to Mössbauer spectroscopy, the inhomogeneous distribution of Cr contributes to magnetic dilution, thus appearing the coexistence of singlet and sextet. Simultaneously, the rare superparamagnetic relaxation appears due to "critical superparamagnetism" caused by small magnetic clusters with intervening sizes. Oxygen vacancies of synthesized sample are also found. The DC magnetization curve reveals the magnetization reversal phenomenon, which is related to the competition between the Dzyaloshinsky–Moriya interaction (DMI) and the magnetic anisotropy belonging to single ions. At 300 K, LCFO reveals weak magnetism. No magnetic transition is observed below 400 K. [ABSTRACT FROM AUTHOR]

Herein, a citric acid combustion method is used to prepare LaFeO3 (LFO) and LaFe0.5Cr0.5O3 (LFCO). Stable and distorted perovskite structures are detected by X‐ray diffraction (XRD) patterns of both samples. Due to the substitution of chromium ions, Fe–Fe couplings are wholly disrupted, thus indicating the transition from a sextet to a singlet at room temperature. The M versus T curve of LFO exhibits two anomalous peaks related to Fe–O–Fe superexchange interactions. However, a quite different behavior is observed in LFCO. It reveals the negative irreversibility below 239 K and becomes paramagnetic above 269 K. The field‐cooled (FC) curve of LFCO is also simulated using the Monte Carlo method with Heisenberg model. Exchange coupling and anisotropy constants, which indicate some system properties, are calculated by applying the particle swarm algorithm fitting. The Néel temperature of LFCO is determined to be 80 K. [ABSTRACT FROM AUTHOR]

Herein, a citric acid combustion method is used to prepare LaFeO3 (LFO) and LaFe0.5Cr0.5O3 (LFCO). Stable and distorted perovskite structures are detected by X‐ray diffraction (XRD) patterns of both samples. Due to the substitution of chromium ions, Fe–Fe couplings are wholly disrupted, thus indicating the transition from a sextet to a singlet at room temperature. The M versus T curve of LFO exhibits two anomalous peaks related to Fe–O–Fe superexchange interactions. However, a quite different behavior is observed in LFCO. It reveals the negative irreversibility below 239 K and becomes paramagnetic above 269 K. The field‐cooled (FC) curve of LFCO is also simulated using the Monte Carlo method with Heisenberg model. Exchange coupling and anisotropy constants, which indicate some system properties, are calculated by applying the particle swarm algorithm fitting. The Néel temperature of LFCO is determined to be 80 K. [ABSTRACT FROM AUTHOR]

In this work, BiFe 1 − x Co x O 3 (x = 0, 0.08) nanoparticles were synthesized by the solution method and their structural differences were studied. X-ray diffraction results show that the rhombohedral R3c space group and perovskite structures are detected in both samples, accompanied by an impurity phase. The (104) and (110) peaks merge when cobalt ions are doped. The decrease in lattice parameters indicates that the microstructure of the nanoparticles becomes gradually distorted. Mössbauer spectroscopy analysis at room temperature reveals an additional doublet due to the oxygen vacancies in BiFe 0. 9 2 Co 0. 0 8 O 3 . Hyperfine interactions, spatial spin-modulated structures and oxygen deficiencies around iron ions are also reflected in the observed spectra and variations in hyperfine parameters. [ABSTRACT FROM AUTHOR]