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Recently, a high mobility quasi-two-dimensional electron gas has been reported for the heterointerface between two insulating and nonmagnetic oxides of spinel γ-Al2O3 and perovskite SrTiO3 (STO). Herein, we fabricated the epitaxial heterostructure with Al-based magnetic spinel oxide MAl2O4 (M = Fe, Co, Ni) on perovskite STO. Remarkably, all the MAl2O4 (M = Fe, Co, Ni) films exhibit ferromagnetic behavior up to room temperature. Although FeAl2O4/STO is insulating, the NiAl2O4/STO and CoAl2O4/STO heterointerfaces are found to be highly metallic and exhibit the anomalous Hall effect (AHE) at temperatures below 30 K. Their Hall mobility is as high as 3 × 104 cm2 V−1 s−1, comparable to that of the γ-Al2O3/STO interface. There has been evidence of oxygen-vacancy-related magnetism in γ-Al2O3/STO at temperatures below 5 K, while the enhanced AHE in NiAl2O4/STO and CoAl2O4/STO likely comes from the magnetic proximity effect induced by the top ferromagnetic MAl2O4 spinel films. [ABSTRACT FROM AUTHOR]

We use powder X-ray diffraction to evaluate the temperature dependence of the crystalline properties during the magnetic phase transition of La(Fe,Mn,Si)13Hz as a function of the Fe/Mn/Si ratio. Both the paramagnetic and ferromagnetic phases were observed as peak overlaps in the patterns around the Curie temperature (TC) occurring continuously in a temperature range of about 5K around TC. Using the Williamson-Hall method, we evaluate the strain developing in the crystallites during the transition and find that it is associated with the growth of the paramagnetic phase as the transition occurs. Based on our measurements and microstructure analyses, we propose that cracking during the phase transition is due to or aggravated by the small content of a La-rich phase. [ABSTRACT FROM AUTHOR]

We use powder X-ray diffraction to evaluate the temperature dependence of the crystalline properties during the magnetic phase transition of La(Fe,Mn,Si)13Hz as a function of the Fe/Mn/Si ratio. Both the paramagnetic and ferromagnetic phases were observed as peak overlaps in the patterns around the Curie temperature (TC) occurring continuously in a temperature range of about 5K around TC. Using the Williamson-Hall method, we evaluate the strain developing in the crystallites during the transition and find that it is associated with the growth of the paramagnetic phase as the transition occurs. Based on our measurements and microstructure analyses, we propose that cracking during the phase transition is due to or aggravated by the small content of a La-rich phase. [ABSTRACT FROM AUTHOR]