Nonequilibrium magnetic properties in oxygen-rich LaMnO₃ nanoparticles

Abstract

Nonequilibrium magnetic properties of oxygenrich LaMnO 3.21 nanoparticles have been investigated by comprehensive magnetic measurements. The composition falls in the metamagnetic canted spin region of the magnetic phase diagram. However, the zerofield cooling memory effect and frequencydependent AC susceptibility reveal a reentrant glassy state at low temperature. In contrast to the superspin glass or cluster glass that reenter from the hightemperature ferromagnetic state in previous studies, analyses based on the power law and Vogel-Fulcher law indicate strongly a conventional spin glass nature. As the magnetic field increases, an anomalous enhancement of the irreversible temperature is observed, suggesting a fieldinduced nonequilibrium magnetic state. These results can be understood by considering the interaction between the antiferromagnetic clusters and the metamagnetic cantedspin matrix inside the nanoparticles.

Spray-Flame Synthesis of LaMnO3+δ Nanoparticles for Selective CO Oxidation (SELOX)

“…The Fourier-transform infrared (FTIR) spectra were obtained from the average of 32 scans recorded in ∼1.7 min (∼3.2 s/scan) from 400 to 4000 cm –1 with a resolution of 4 cm –1 by using a Bruker Vertex 80 with standard optical components (KBr beam splitter, DigiTect DLaTGS detector, attenuated total reflectance (ATR) sample holder). Ultraviolet–visible (UV–VIS) spectra were recorded from 200 to 800 nm with a high-performance dual-beam Varian Cary 400 spectrophotometer (silica overcoated optics, Schwarzschild coupling optics, PbS detector) using a scan rate of 600 nm min – and a step size of 1 nm.…”

“…Lanthanum-containing manganites (LaMnO 3 ) are perovskite-type oxides that have been studied over the years for their diverse and interesting magnetic and electrochemical properties, e.g., colossal magnetoresistance in doped manganites , and high-energy storage and power densities in Li-ion batteries. , Recently, these compounds also attracted growing attention for their versatile catalytic properties combined with chemical stability, especially regarding their potential as low-cost substitutes of noble-metal catalysts for environmentally relevant reactions as CO oxidation and CO selective oxidation (SELOX). − They can be applied for, e.g., removing CO from enclosures and residue gases to avoid the poisoning of catalysts in proton-exchange membrane fuel cells for H 2 production. , …”

Study of AC Susceptibility of La0.8Sr0.2MnO3 at Different Frequencies

“…The Tc of La0.8Sr0.2MnO3sample is 326K and 336K at 100Hz and 500Hz respectively. This suggests that the freezing out of domain wall dynamics is linked to the frequency dependence of ac susceptibility [16]. Inhomogeneities, defects, interstitials, and realignments of electron states within the domain walls may be the cause of frequency dependent mobility of the domain walls [13].…”