Magnetism in a Spintronic Compound Zr_0.8Cr_0.2O₂ of Small Crystallites

Abstract:

A transition metal ion Cr⁴⁺(3d² spins) doped ZrO₂ of small crystallites presents tailored magnetic, electrical and optical properties useful for magnetodielectric and spintronic applications. A liquid polymer precursor gel (Cr⁴⁺ and Zr⁴⁺ complex with glycerol) when heated in an autoclave at a small pressure 0.6-0.7 atm at 420–470 K results in a compound Zr_0.8Cr_0.2O₂ with an average 5 nm crystallite size of a stabilized cubic (c)-ZrO₂-type phase (after 2 h annealing at 773 K in air). A broad Raman band is observed at ~300 cm^-1 in acoustic and transverse optic phonons characteristic of the c-ZrO₂-type structure, with a prominent O–Cr–O stretching band at 878 cm^-1 in a ferromagnetic order. A CrO₂/Cr₂O₃ surface layer exhibits two weak bands at ~1011 cm^-1 and 1032 cm^-1. The sample exhibits an ‘S’-shaped ferromagnetic hysteresis loop (does not saturate below 60 kOe fields) at 5 K, with a magnetization M = 85.79 emu/g (in the CrO₂ part) at 60 kOe and coercivity H_c = 100 Oe. With warming above 5 K, the loop converges progressively with only a weak ferromagnetism at room temperature, M = 9.08 emu/g and H_c = 54.2 Oe. As a pinning barrier, the uncompensated spins in the surface layer supports coercivity at low temperature. A model magnetic structure describes the magnetic properties in correlation to the microstructure.

• Periodical: Journal of Nano Research (Volume 28)
• Pages: 101-108
• DOI: https://doi.org/10.4028/www.scientific.net/JNanoR.28.101
• Online since: June 2014
• Authors: Arundhati Sengupta*, Susmita Misra, Shanker Ram
• Keywords: Magnetic Property, Nanostructure, Spintronic Oxides

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