Oxidation-controlled magnetism and Verwey transition in Fe/Fe

Tóm tắt

The structural and magnetic properties of Fe/Fe 3 O 4 nanocomposites, synthesized by combined high energy ball milling and controlled oxidation, have been studied. An X-ray diffraction analysis of the crystal structure of the nanocomposites confirmed the coexistence of Fe and Fe 3 O 4 phases. An increase of the oxygen concentration during oxidation process led to the formation of a higher fraction of the Fe 3 O 4 phase with good crystallinity and stoichiometry. The morphology of the nanocomposites revealed a lamella-like structure with a thickness of about 30 nm. The saturation magnetization decreased when the phase fraction of Fe 3 O 4 increased. The coercivity was enhanced at low temperatures (≤100 K) but decreased at high temperatures, due to thermal fluctuation effects on the anisotropy in the Fe 3 O 4 phase. Interestingly, the lamellae exhibited a sharp Verwey transition near 120 K, which is often suppressed or absent in nanostructured Fe 3 O 4 due to the poorly crystalline, off-stoichiometric characteristic. The temperature dependence of high-field magnetization of the lamellae is analyzed by the modified Bloch law. Our study demonstrates the possibility of tuning the magnetism in iron/iron oxide nanosystems through controlled oxidation.

Từ khoá

Lamellar structure; Fe/Fe; 3; O; 4; nanocomposites; Oxidation-controlled magnetism; Verwey phase transition; Modified Bloch law

Tài liệu tham khảo

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