Ferromagnetism in metal oxide systems: interfaces, dopants, and defects

Abstract

Ferromagnetism in metal oxide systems has always attracted scientific attention in view of the intriguing and interesting interplay of spin, charge, orbital and lattice degrees of freedom that such systems display.This trend appears to be continuing with enhanced focus on interface systems, multiferroics, diluted magnetic semiconducting oxides (DMSOs) and nanomaterial magnetism. Newer techniques are being applied to bring out materials issues that are critical to the precise understanding of the origin of magnetism in certain cases. Interest is also beginning to grow in exploring application potential of some such systems. In this article we review the developments in this field by late 2011 and 2012.

Correlating defect induced ferromagnetism and gas sensing properties of undoped tin oxide sensors

“…The as-prepared combustion synthesized SnO 2 shows high saturation magnetization of $0.018 emu/g as compared to $0.002 and $0.0005 emu/g in annealed samples and SnO 2 prepared by precipitation, respectively. This unintentional magnetization in non-magnetic (non-transition metal oxide) systems like SnO 2 is known to originate from the oxygen vacancies in the crystal which has been confirmed by many researchers [9][10][11]15,16,[20][21][22][23] and is evident in this system using various characterization techniques like Photoluminescence (PL) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy as reported in our previous studies. 17,18 This defect induced ferromagnetism has been found to reduce remarkably upon annealing the as-synthesized combustion product (TO) at higher temperatures (TO800) as a result of structural ordering which leads to the reduction in bulk as well as surface oxygen vacancy concentration.…”

“…This equilibrium method of synthesis is expected to show lesser amount of defects. 18 In TO sample, high defect density is exhibited due to non-equilibrium processing conditions inherent to the solution combustion methods and, hence, exhibits high magnetization originating from F centers in the crystal, 16,20,31 which yielded a yellow color to the as-synthesized product. 18 In the high temperature annealed sample (TO800), the structural defects are diminished as a result of structural relaxation due to the thermal treatment, and hence, the magnetization reduces.…”

Fe-induced morphological transformation of 1-D CuO nanochains to porous nanofibers with enhanced optical, magnetic and ferroelectric properties

“…14,15 Bulk CuO is known to exhibit antiferromagnetic 16 and multiferroic behavior at low temperature. 19 CuO was earlier synthesized in different dimensions (1-D, 2-D, 3-D), but 1-D nanostructures assume significant importance in regard to their increased efficiency in the transport of electrons and controlled optical and magnetic behavior which have applications in solar cells, 20,21 sensors, [22][23][24] FETs, 25 the next generation Na-ion batteries 26 and spintronic devices. 19 CuO was earlier synthesized in different dimensions (1-D, 2-D, 3-D), but 1-D nanostructures assume significant importance in regard to their increased efficiency in the transport of electrons and controlled optical and magnetic behavior which have applications in solar cells, 20,21 sensors, [22][23][24] FETs, 25 the next generation Na-ion batteries 26 and spintronic devices.…”

Carbon induced magnetism of SnO2 surfaces

“…[34,35] It is well known that the surface confinement effect is important to shape up the magnetic properties of SnO 2 . [36,37] The reduced symmetry and changed boundary conditions play important role in the magnetism of materials with reduced dimensions. [20,38] Therefore investigations on SnO 2 surface magnetism are important.…”