Room-temperature ferromagnetism in Co doped La2O3

Abstract

Single-phase La2(1−x)Co2xO3−δ polycrystalline samples with x=0%–8% were synthesized by the conventional ceramic method, and the effect of Co content on the magnetic behaviors has been systemically investigated. X-ray diffraction and x-ray photoelectron spectroscopy studies indicate no Co metal clusters or secondary magnetic phases in any samples in this study. It is found that the undoped or slightly doped samples show no ferromagnetic signal, while samples with x in the range of 0.5%–2% exhibit an exponential increase of saturation magnetization (Ms) as a function of Co concentration. When x increases beyond 2%, an inverse correlation between the magnetization and Co content was observed. We reported an Ms as large as 0.05emu∕g and a Curie temperature above RT in our samples, rendering Co:La2O3 a candidate diluted magnetic oxide for RT applications. Our results also strongly support the oxygen vacancy (F-center) mediated mechanism for RT ferromagnetism in transition-metal doped high-k oxides

Steering the Ester and γ-Valerolactone Selectivities in Levulinic Acid Hydrogenation

“…190344), respectively, of orthorhombic endcentered Co 3 La 2 phases. Some of the peaks were slightly shifted from their original 2θ values because some of the La atoms were substituted by Co atoms 16. The acidity and basicity of the catalyst as determined by NH 3 -TPD and CO 2 -TPD (discussed later) were due to the Co−La and La(OH) 3 phases, which played important roles in directing the selectivity to GVL in levulinic acid hydrogenation.In the case of the Cu/La2 O 3 sample, peaks at 2θ = 48.5°( 202), 51.3°(112), 53.4°(020), and 61.4°(113) were assigned to the monoclinic end-centered CuO phase (JCPDF file no.…”

A multi-analytical methodology for the characterization of industrial samples of spent Ni-MH battery powders

“…2) b) and d). La 2 O 3 , Nd 2 O 3 and Pr 2 O 3 are diamagnetic and paramagnetic and can therefore not be quantified using magnetic susceptibility (Sala et al, 2018;Wen et al, 2008). The phase assemblage of cluster 2 is also in good accordance with the CeO 2 phase identified both by magnetic susceptibility and powder XRD (Figure SI-2) a) and Fig.…”

Effects of oxygen vacancies on the room-temperature ferromagnetism of Co-doped polycrystalline CeO2

“…Recently, room-temperature ferromagnetism (RT-FM) has been frequently reported in transition-metal (TM)-doped semiconducting [1][2][3][4] or insulating [5][6][7] oxides, which are known as diluted magnetic oxides (DMO). However, the intrinsic origination of the RT-FM remains controversial.…”

“…However, the intrinsic origination of the RT-FM remains controversial. As the carrier-induced FM mechanism [1] is usually used to explain the FM in semiconducting oxides, the high-temperature FM obtained in TM-doped insulating oxides such as HfO 2 [5], CeO 2 [6], and La 2 O 3 [7] refers to an oxygen vacancy (Vo)-mediated FM mechanism [3,8]. As important evidences, it has been reported that annealing the TM-doped oxide in reduction atmosphere (H 2 flow or vacuum) distinctly enhanced its magnetization [9][10][11], while annealing in oxidation atmosphere (air or oxygen flow) could significantly depress the RT-FM [12][13][14].…”