Browsing by Author "Li, S"
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- ItemDevelopment of advanced diluted magnetic semiconductors with rare earth doping technology(University of Western Australia, 2007-10-15) Photongkam, P; Ionescu, M; Zeng, R; Yu, DH; Li, S
- ItemDoping of ZnO thin film with Eu using ion beams(Trans Tech Publications, 2010-01-01) Ionescu, M; Photongkam, P; Yu, DH; Siegele, R; Li, S; Cohen, DDModification of electric and magnetic properties of ZnO thin films was achieved by low energy Eu ion irradiation. The desired doping levels as well as the depth distribution of the dopant was controlled by the ion energy and the ion flux, following a simulated interaction between the doping ion and the host ZnO matrix of epitaxial ZnO (0001) films of approximatelly 200nm, grown on c-Al2O3 by PLD. The properties of the doped ZnO film depend in a critical way on the homogeneity of the doped ions throughout the entire film. The doping levels and the depth distribution of dopants were measured by elastic recoil detection analysis (ERDA). The results show a uniform depth distribution of Eu, as well as some level of Al diffusion from the substrate and the presence of some low levels of H, N and O. PACS code: 68.49Sf; 74.78Bz.
- ItemElectron doping effects on the spin spectroscopy of BaFe2-xNixAs2 superconductors(International Conference on Neutron Scattering, 2017-07-12) Luo, H; Gong, D; Xie, T; Lu, X; Kamazawa, K; Iida, K; Kajimoto, R; Ivanov, AS; Adroja, DT; Kulda, J; Danilkin, SA; Deng, G; Li, S; Dai, PHigh-temperature superconductivity in iron pnictides emerges from electron or hole doped parent compounds with antiferromagnetic order, which is argued to be associated with both the presence of high-energy spin excitations and a coupling between low-energy spin excitations and itinerant electrons . With more than 6 years\' efforts, we have used time-of-flight neutron spectroscopy to extensively map out the spin excitations in the electron-doped BaFe2-xNixAs2 especially around the overdoped zone boundary of superconductivity. We have found that the high energy spin fluctuations survive in the extremely high doping x=0.6 far beyond the superconducting dome , but the low energy spin excitations including the spin resonance mode is very sensitive to the electron dopings , by finally forming a large spin gap just after the disappearance of superconductivity in the overdoped regime . Further polarized neutronanalysis indicate that the spin gap actually is anisotropic, and the longitudinal mode of spin fluctuations, as a hallmark of the itinerant magnetism from Fermi surface nesting , is totally eliminated together with the hole pockets near the electron-overdoped zone boundary of superconductivity .Our results suggest that the strong fluctuations from local moments give framework for magnetic interaction, while itinerant spin excitations originated from Fermi surface nesting are crucial to the superconductivity in iron pnictides.
- ItemElectron doping evolution of the anisotropic spin excitations in BaFe(2-x)NixAs2(Americal Physical Society, 2012-07-10) Luo, H; Yamani, Z; Chen, YC; Lu, X; Wang, M; Li, S; Maier, TA; Danilkin, SA; Adroja, DT; Dai, PWe use inelastic neutron scattering to systematically investigate the Ni-doping evolution of the low-energy spin excitations in BaFe(2-x)NixAs2 spanning from underdoped antiferromagnet to overdoped superconductor (0.03 <= x <= 0.18). In the undoped state, BaFe2As2 changes from paramagnetic tetragonal phase to orthorhombic antiferromagnetic (AF) phase below about 138 K, where the low-energy (<=similar to 80 meV) spin waves form transversely elongated ellipses in the [H, K] plane of the reciprocal space. Upon Ni doping to suppress the static AF order and induce superconductivity, the c-axis magnetic exchange coupling is rapidly suppressed and the momentum distribution of spin excitations in the [H, K] plane is enlarged in both the transverse and longitudinal directions with respect to the in-plane AF ordering wave vector of the parent compound. As a function of increasing Ni-doping x, the spin excitation widths increase linearly but with a larger rate along the transverse direction. These results are in general agreement with calculations of dynamic susceptibility based on the random phase approximation (RPA) in an itinerant electron picture. For samples near optimal superconductivity at x approximate to 0.1, a neutron spin resonance appears in the superconducting state. Upon further increasing the electron doping to decrease the superconducting transition temperature T-c, the intensity of the low-energy magnetic scattering decreases and vanishes concurrently with vanishing superconductivity in the overdoped side of the superconducting dome. Comparing with the low-energy spin excitations centered at commensurate AF positions for underdoped and optimally doped materials (x <= 0.1), spin excitations in the overdoped side (x = 0.15) form transversely incommensurate spin excitations, consistent with the RPA calculation. Therefore, the itinerant electron approach provides a reasonable description to the low-energy AF spin excitations in BaFe(2-x)NixAs2. © 2012, American Physical Society.
- ItemEnhancement of co substitution induced by Eu codoping in ZnO-based diluted magnetic semiconducting thin films(American Institute of Physics, 2010-02) Photongkam, P; Zhang, YB; Assadi, MHN; Li, S; Yu, DH; Ionescu, M; Pan, AVTo avoid the occurrence of doped magnetic ion clustering is a challenge in fabrication of diluted magnetic semiconductors (DMSs). In this work, we report the intrinsic ferromagnetic behavior in Co-doped ZnO DMSs induced by Eu codoping. Both structural parameters and magnetic properties demonstrate the existence of an interaction between Co and Eu ions. The observation of multiplet structures for the localized Co 3d states in x-ray absorption and x-ray magnetic circular dichroism characterization evidences that the codoped Eu plays an important role in facilitating the Co substitution of Zn, leading to intrinsic ferromagnetism. © 2010, American Institute of Physics
- ItemFabrication and characterisation of diluted magnetic semiconductors thin films using ion beams(Trans Tech Publication Inc., 2012-01-01) Ionescu, M; Photongkam, P; Siegele, R; Deslandes, A; Li, S; Cohen, DDThe intrinsic n-type (II-VI) semiconductor ZnO may become ferromagnetic at room temperature, by small additions of magnetic ions, resulting in what is called a Diluted Magnetic Semiconductors (DMS). The potential application of DMS in spintronic devices of is driving the research effort to dope magnetic elements into this semiconductors with a depth distribution as uniform as possible. The doping levels and the depth distribution of dopants are critical parameters for the magnetic properties of this material and the possible clustering of dopants can play a significant negative role in its macroscopic magnetic properties. Thin ZnO (0001) films of between 100nm and 500nm, grown on c-Al2O3 by MOCVD were implanted with Co, Eu and Co+Eu by ion irradiation at low energies. In order to improve the depth distribution of dopants, the ion implantation was carried out through a number of appropriately chosen range foils. The results show an increase in the level of dopant homogeneity throughout the entire thickness of the film, and a ferromagnetic behavior above room temperature for Zn0.96Co0.04O, Zn0.96Eu0.04O and Zn0.92Co0.04Eu0.04O. © 2012, Trans Tech Publications
- ItemFerromagnetic ordering in Mn-doped ZnO nanoparticles(Springer, 2014-01-01) Luo, X; Lee, W-T; Xing, G; Bao, N; Yonis, A; Chu, D; Lee, J; Ding, J; Li, S; Yi, JZn1 - xMn x O nanoparticles have been synthesized by hydrothermal technique. The doping concentration of Mn can reach up to 9 at% without precipitation or secondary phase, confirmed by electron spin resonance (ESR) and synchrotron X-ray diffraction (XRD). Room-temperature ferromagnetism is observed in the as-prepared nanoparticles. However, the room-temperature ferromagnetism disappears after post-annealing in either argon or air atmosphere, indicating the importance of post-treatment for nanostructured magnetic semiconductors.© 2014 Luo et al.; licensee Springer.
- ItemFerromagnetism of Co, Eu Co-doped ZnO and 5%-Co doped TiO2 magnetic semiconductors(Australian Institute of Physics, 2014-02-04) Lee, OJ; Lou, X; Lee, WT; Lauter, V; Triani, G; Li, S; Yi, JBDiluted magnetic semiconductor has attracted wide interest due to its potential applications in spintronics devices. Oxide semiconductor based diluted magnetic semiconductors has been investigated in detail for possible ferromagnetism above room temperature. However, most of the diluted magnetic semiconductors show very weak ferromagnetism. The magnetic moment is originated from the doped magnetic element, such as Fe, Co, Ni. Rare-earth element, which shows strong spin-orbit coupling, may enhance the magnetic anisotropy of the diluted magnetic semiconductors, thus enhances the ferromagnetism. In this work, we used both Co and Eu to co-dope ZnO and deposited Co doped TiO2 thin films in order to achieve a diluted room-temperature magnetic semiconductor with strong ferromagnetism. 4%Co and 4%Eu or 6% Eu were used for the doping by implantation in ZnO and 5%Co-TiO2 film were deposited on LaAlO3 substrate under different oxygen partial pressures from 10-4 to 10-6 torr. For the ZnO-based thin films, XRD analysis indicates there is no secondary or impurity phase. Magnetic measurement by SQUID shows room temperature ferromagnetism. Polarized neutron reflectometry (PNR) analysis illustrates that ZnO film is 100 nm in thickness and the magnetic layers is around 30 nm, which is in consistent with the penetration depth of Co and Eu implantation, indicating the magnetic moment is due to the Co and Eu co doping. 4%Co, 4%Eu codoped ZnO film has a saturation magnetization of 3.57 emu/cm3, while 4%Co, 6%Eu co doped ZnO film has a saturation magnetization of 9.62 emu/cm3, indicating the significant enhancement of saturation magnetization by more rare earth element doping. For the TiO based thin films, XRD analysis show epitaxial growth and that the films have anatase phases. TEM confirms the single crystal like microstructure. EDX mapping indicates that Co is uniformly distributed in the TiO2 matrix, suggesting effective doping of Co dopant. Magnetic measurement shows that film deposited under lower oxygen partial pressure has a larger saturation magnetization. PNR shows that the magnetization is uniformly distributed along the film thickness. The magnetization for the film deposited under an oxygen partial pressure of 10-6 torr is about 4.2 emu/cm3, which is much smaller than that measured by SQUID (30 emu/cm3). This suggests a magnetic dead layer on the film surface.
- ItemImmobilization of Na ions for substantial power factor enhancement: site-specific defect engineering in Na0.8CoO2(American Chemical Society, 2012-02-16) Tsai, PH; Assadi, MHN; Zhang, T; Ulrich, C; Tan, TT; Donelson, R; Li, SSimultaneous enhancement of the interdependent Seebeck coefficient and electrical conductivity has been achieved through defect engineering by doping Mg into specific sites of Na0.8CoO2. Results from thermoelectric measurement demonstrate that the power factor was substantially increased by 50% at ambient. Experimental and theoretical analyses show that the occupation of divalent Mg in the disordered Na layer immobilizes the Na ions and thus induces a long-range ordering of Na ions. This phenomenon improves the carrier mobility significantly, giving rise to the observed exotic thermoelectric performance. Moreover, it is predicted that other electronically closed-shell dopants in sodium cobaltate play a similar role in enhancing the thermoelectric conversion efficiency. © 2012, American Chemical Society.
- ItemKey role of Bismuth in the magnetoelastic transitions of Ba3BiIr2O9 and Ba3BiRu2O9 as revealed by chemical doping(America Chemical Society, 2013-12-24) Blanchard, PER; Huang, Z; Kennedy, BJ; Liu, S; Miiller, W; Reynolds, EM; Zhou, Q; Avdeev, M; Zhang, Z; Aitken, JB; Cowie, BCC; Jang, LY; Tan, TT; Li, S; Ling, CDThe key role played by bismuth in an average intermediate oxidation state in the magnetoelastic spin-gap compounds Ba3BiRu2O9 and Ba3BiIr2O9 has been confirmed by systematically replacing bismuth with La3+ and Ce4+. Through a combination of powder diffraction (neutron and synchrotron), X-ray absorption spectroscopy, and magnetic properties measurements, we show that Ru/Ir cations in Ba3BiRu2O9 and Ba3BiIr2O9 have oxidation states between +4 and +4.5, suggesting that Bi cations exist in an unusual average oxidation state intermediate between the conventional +3 and +5 states (which is confirmed by the Bi L3-edge spectrum of Ba3BiRu2O9). Precise measurements of lattice parameters from synchrotron diffraction are consistent with the presence of intermediate oxidation state bismuth cations throughout the doping ranges. We find that relatively small amounts of doping (∼10 at%) on the bismuth site suppress and then completely eliminate the sharp structural and magnetic transitions observed in pure Ba3BiRu2O9 and Ba3BiIr2O9, strongly suggesting that the unstable electronic state of bismuth plays a critical role in the behavior of these materials. © 2013, American Chemical Society.
- ItemMagnetic structure and properties of the rechargeable battery insertion compound Na2FePO4F(American Chemical Society, 2013-12-26) Avdeev, M; Ling, CD; Tan, TT; Li, S; Oyama, G; Yamada, A; Barpanda, PThe magnetic structure and properties of sodium iron fluorophosphate Na2FePO4F (space group Pbcn), a cathode material for rechargeable batteries, were studied using magnetometry and neutron powder diffraction. The material, which can be described as a quasi-layered structure with zigzag Fe-octahedral chains, develops a long-range antiferromagnetic order below ∼3.4 K. The magnetic structure is rationalized as a super-exchange-driven ferromagnetic ordering of chains running along the a-axis, coupled antiferromagnetically by super-super-exchange via phosphate groups along the c-axis, with ordering along the b-axis likely due to the contribution of dipole–dipole interactions. © 2013 American Chemical Society
- ItemManipulation of planar oxygen defect arrangements in multifunctional magnèli titanium oxide hybrid systems: from energy conversion to water treatment(Royal Society of Chemistry, 2020-10-28) Liu, YC; Yang, J; Liu, Y; Zheng, J; Lee, W; Shi, JJ; Horlyck, J; Xie, JZ; Tay, YY; Tan, TT; Yu, DH; Mole, RA; McIntyre, GJ; Zhang, CY; Toe, CY; Waite, TD; Scott, J; Wang, Y; Wu, T; Han, SH; Li, SAn extremely close relationship exists between energy usage and water supply with a tremendous amount of energy being consumed to process water for drinking and other purposes. The current energy crisis and inefficient water management place enormous stress on the sustainability of our society and environment. As such, the development of high-efficiency, cost-effective, and environmentally friendly materials which possess co-existing functionalities for applications ranging from energy capture to water treatment in one material, provides an opportunity to achieve sustainable development. As multifunctional materials, the layer-structured Magnèli titanium oxides with stoichiometry of TinO2n−1 (n ≥ 2) have been extensively studied in view of their potential for photocatalytic, thermoelectric and photothermal applications over the past few years. This group of materials occurs naturally as layered structures with planar oxygen defects, however, understanding of the correlation between the planar arrangements of the oxygen defects and various energy-related properties remains limited. Here, we demonstrate how the formation of layer structured TinO2n−1 with various planar oxygen defect arrangements correlates with the changes of their physical and chemical properties. The experimental results from inelastic neutron scattering analysis and electrical characterizations provide evidence that the planar oxygen defects are responsible for phonon scattering and exert a strong influence on their electrical conductivities. Manipulating these planar defects allows interconversion between different phases, which changes the interplay between electronic and phononic sub-systems. These manipulations potentially enable optimization of the corresponding physical properties of these materials such that they are rendered suitable for applications that require co-operative multifunctionality. More specifically, the experimental results demonstrate that the valence band positions and the onset potentials in the materials are raised, further enhancing their ability for catalysis of electrochemical reactions. This work also demonstrates the combinational effects of the thermoelectric and photothermal properties of these materials on their photocatalytic and electrochemical performance thereby providing a novel means of controlling the multi-response functionality of these materials for a variety of applications in different environments. © The Royal Society of Chemistry 2020
- ItemNeutron Laue diffraction study of the complex low-temperature magnetic behaviour of brownmillerite-type Ca2Fe2O5(International Union of Crystallography, 2015-01-01) Auckett, JE; McIntyre, GJ; Avdeev, M; De Bruyn, H; Tan, TT; Li, S; Ling, CDThe atomic and magnetic structure of brownmillerite Ca2Fe2O5 has been refined against single-crystal neutron Laue diffraction data collected at 300, 100 and 10 K under zero-field and low-magnetic field (35 Oe = 35 × 103/4[pi] A m-1) conditions. Ca2Fe2O5 is a canted G-type antiferromagnet with Pcm'n' symmetry, the magnetic moments on Fe being directed approximately along the crystallographic c axis at room temperature. The refinement results show clearly that this magnetic structure persists down to T = 10 K, despite a previous suggestion that an anomalous magnetic susceptibility enhancement observed in Ca2Fe2O5 single crystals between 40 and 140 K might signify a reorientation of the antiferromagnetic easy axis from c to a below 40 K. Alternative explanations for this susceptibility anomaly are considered in terms of the evidence for partial or short-range loss of order in the anomalous regime, possibly due to the presence of multiple competing sublattice interactions. © International Union of Crystallography
- ItemNovel synthesis and thermal property analysis of MgO–Nd2Zr2O7 composite(Elsevier, 2016-11-15) Kong, L; Zhang, J; Maeda, Y; Blackford, MG; Li, S; Triani, G; Gregg, DJMgO-Nd2Zr2O7composites with ratios of 50–70 vol% MgO were produced via a one-pot combustion synthesis. A suite of characterization techniques, including X-ray diffraction, scanning and transmission electron microscopy were employed to investigate the structural properties while dilatometry, simultaneous thermal analysis and laser flash analysis were used to characterize the thermal properties of the composites. Dense pellets were produced after sintering at 1400 °C with grain sizes between 200 and 500 nm for both phases. The thermal properties of the composites are similar to those produced using standard methods. The composite with 70 vol% MgO was found to have the highest thermal conductivity below 1000 °C, while above this temperature the thermal conductivity was found to be similar and independent of MgO content. This novel synthesis route produces materials which show significant improvements in homogeneity with smaller particle sizes when compared to current standard synthesis techniques without significantly reducing thermal conductivity. © 2016 Elsevier Ltd.
- ItemOxygen level dependent lattice dynamics of Na0.73CoO2-δ.(American Chemical Society, 2010-11-22) Tsai, PH; Donelson, R; Tan, TT; Avdeev, M; Yu, DH; Strassle, T; Li, SThe optical and acoustic phonon branches of Na0.73CoO2-δ have been determined using Raman scattering and inelastic neutron scatterings, and their correlation with phononic thermal conductivity kph in terms of oxygen-vacancy concentration δ was investigated. The experimentally observed phonon stiffening of the Raman-active E1g mode suggests that oxygen vacancies may help stabilize texturing of Na ions that gives rise to higher kph with increasing δ. The generalized phonon density of states characterized using inelastic neutron scattering exhibits subtle stiffening of acoustic and optical phonons with δ, which appears to be responsible for the variations in kph(T) profile in the temperature range 323−923 K. © 2010, American Chemical Society
- ItemOxygen nonstoichiometry in (Ca2CoO3)0.62(CoO2): a combined experimental and computational study(American Chemical Society, 2014-07-28) Schrade, M; Casolo, S; Graham, PJ; Ulrich, C; Li, S; Løvvik, OM; Finstad, TG; Norby, TThe oxygen nonstoichiometry in the misfit calcium cobaltite (Ca2CoO3)0.62(CoO2) has been studied experimentally and by density functional theory (DFT) calculations. The standard oxidation enthalpy ΔH0Ox of oxygen deficient (Ca2CoO3)0.62(CoO2) was measured directly using simultaneous thermogravimetry and differential scanning calorimetry. ΔH0Ox was found to be in agreement with the prediction from a previously published defect chemical model based on purely thermogravimetrical analysis. A series of samples with different oxygen vacancy concentration was prepared by annealing in air, followed by rapid quenching. Room-temperature Raman spectroscopy showed a sharp mode at 700 cm–1 decreasing in intensity with increasing vacancy concentration. We discuss this observation as evidence for oxygen vacancies being preferably formed within the central layer of the Ca2CoO3 subsystem. DFT calculations demonstrated that the calculated electronic structure is sensitive to the chosen model of the crystal structure. Still, for all investigated models, the standard formation enthalpy of oxygen vacancies within the Ca2CoO3 moiety was much lower than that for a site within the CoO2 layer, in agreement with the presented experimental data. © 2014, American Chemical Society.
- ItemReversible hydrophobic to hydrophilic transition in graphene via water splitting induced by UV irradiation(Macmillan Publisher, 2014-09-01) Xu, Z; Ao, Z; Chu, D; Younis, A; Li, CM; Li, SAlthough the reversible wettability transition between hydrophobic and hydrophilic graphene under ultraviolet (UV) irradiation has been observed, the mechanism for this phenomenon remains unclear. In this work, experimental and theoretical investigations demonstrate that the H2O molecules are split into hydrogen and hydroxyl radicals, which are then captured by the graphene surface through chemical binding in an ambient environment under UV irradiation. The dissociative adsorption of H2O molecules induces the wettability transition in graphene from hydrophobic to hydrophilic. Our discovery may hold promise for the potential application of graphene in water splitting. © 2014, Macmillan Publishers Limited
- ItemSpin dynamics of edge-sharing spin chains in SrCa13Cu24O41(American Physical Society, 2018-11-12) Deng, G; Yu, DH; Mole, RA; Pomjakushina, E; Conder, K; Kenzelmann, M; Yano, SI; Wang, CW; Rule, KC; Gardner, JS; Luo, H; Li, S; Ulrich, C; Imperia, P; Ren, W; Cao, S; McIntyre, GJThe low-energy magnetic excitation from the highly Ca-doped quasi-one-dimensional magnet SrCa13Cu24O41 was studied in the magnetic ordered state by using inelastic neutron scattering. We observed the gapless spin-wave excitation, dispersive along the a and c axes but nondispersive along the b axis. Such excitations are attributed to the spin wave from the spin-chain sublattice. Model fitting to the experimental data gives the nearest-neighbor interaction Jc as 5.4 meV and the interchain interaction Ja =4.4meV. Jc is antiferromagnetic and its value is close to the nearest-neighbor interactions of the similar edge-sharing spin-chain systems such as CuGeO3. Comparing with the hole-doped spin chains in Sr14Cu24O41 , which shows a spin gap due to spin dimers formed around Zhang-Rice singlets, the chains in SrCa13Cu24 O41 show a gapless excitation in this paper. We ascribe such a change from gapped to gapless excitations to holes transferring away from the chain sublattice into the ladder sublattice upon Ca doping. ©2018 American Physical Society
- ItemSpin dynamics of quasi-one-dimensional spin-ladder system SrCa13Cu24O41 in the long-range magnetic ordering state(Australian Institute of Physics, 2018-01-31) Deng, G; Yu, DH; Mole, RA; Yano, SI; Wang, CW; Rule, KC; Gardner, JS; Luo, H; Li, S; Ulrich, C; Imperia, P; Ren, W; Cao, S; Pomjakushina, E; Conder, K; Kenzelmann, M; McIntyre, GJSr14-xCaxCu24O41 is a quasi-one-dimensional magnet, which consists of two sublattices: spin ladder and spin chain, forming an incommensurate crystal structure along the c axis, namely, the ladder leg or chain direction. The highly Ca-doped compounds undergo a superconducting phase transition under hydrostatic pressure ~ 3GPa, which is really intriguing since the hole-doped even-leg spin-ladder system was theoretically predicted as superconductors by charge-pairing mechanism through antiferromagnetic interaction on the rungs of spin ladders. In the previous study, we discovered that all compounds with different Ca content have a singlet ground state with a spin-gap ~ 32meV. In the highly Ca-doped sample SrCa13Cu24O41, a long-range magnetic ordering takes place at ~ 4.2K. Interestingly, the singlet spin-liquid state and the long-range magnetic ordering coexist in this compound. In this study, we further investigated its spin dynamics in the ordered phase by using inelastic neutron scattering on PELICAN and SIKA at OPAL. We observed the gapless spin-wave excitation, dispersive along the a and c axes but nondispersive along the b axis, indicating the nature of a 2D magnet. A dynamic model has been proposed to fit the experimental data, indicating three major exchange interactions along rungs (JR), legs (JL) and between neighbor ladders (JInter). This study helps us to understand the origin of the spin liquid ground state in this low-dimensional magnet, in which hole-doping should be attributed to induce the long-range magnetic ordering due to the disorder-induced order effect.
- ItemTailoring the coercivity in ferromagnetic ZnO thin films by 3d and 4f elements codoping(AIP Scitation, 2014) Lee, JJ; Xing, GZ; Yi, JB; Chen, TK; Ionescu, M; Li, SCluster free, Co (3d) and Eu (4f) doped ZnO thin films were prepared using ion implantation technique accompanied by post annealing treatments. Compared with the mono-doped ZnO thin films, the samples codoped with Co and Eu exhibit a stronger magnetization with a giant coercivity of 1200 Oe at ambient temperature. This was further verified through x-ray magnetic circular dichroism analysis, revealing the exchange interaction between the Co 3d electrons and the localized carriers induced by Eu3+ ions codoping. The insight gained with modulating coercivity in magnetic oxides opens up an avenue for applications requiring non-volatility in spintronic devices. © 2014, AIP Publishing LLC.