We studied the electronic and magnetic dynamics of ferromagnetic insulating BaFeO3 thin films by using pump-probe time-resolved resonant x-ray reflectivity at the Fe 2p edge. By changing the excitation density, we found two distinctly different types of demagnetization with a clear threshold behavior. We assigned the demagnetization change from slow (∼ 150 ps) to fast (< 70 ps) to a transition into a metallic state induced by laser excitation. These results provide a novel approach for locally tuning magnetic dynamics. In analogy to heat assisted magnetic recording, metallization can locally tune the susceptibility for magnetic manipulation, allowing to spatially encode magnetic information.PACS numbers: 71.30.+h, 73.61.-r, 75.70.-i, 78.66.-w Control of magnetic states by optical excitations in magnetically ordered materials has attracted considerable attention since the demonstration of ultrafast demagnetization in Ni within 1 ps, explored by timeresolved magneto-optical Kerr effect studies [1]. Ultrafast demagnetization was also observed for other elementary ferromagnetic transition metals such as Co and Fe, and intermetallic alloys [2,3].Several mechanisms have been proposed to understand the ultrafast demagnetization. Beaurepaire et al. proposed a phenomenological "three-temperature model" in order to understand the ultrafast demagnetization of Ni, which considers three interacting reservoirs of electrons, spins, and lattice, and suggested the importance of direct electron-spin interactions. Since the electron, spin, and lattice systems are quite tightly coupled to each other in strongly correlated 3d transition metal oxides, it is interesting to investigate the photoinduced dynamics with respect to the electronic states and magnetism [4][5][6][7][8][9][10][11][12][13][14][15].For this study, we chose fully oxidized single crystalline BaFeO 3 thin films, which show unusual behaviors of ferromagnetic and insulating properties with saturation magnetization and Curie temperature of 3.2 µ B /formula unit and 115 K, respectively [16]. The large magnetic moment of BaFeO 3 thin films results in quite large peak intensity of Fe 2p x-ray magnetic circular dichroism (XMCD), ∼ 18 % of the x-ray absorption peak * Electronic address: wadati@issp.u-tokyo.ac.jp; URL: http://www.geocities.jp/qxbqd097/index2.htm intensity [17]. Thus, BaFeO 3 thin films are appropriate samples to carry out time-resolved magnetic circular dichroism experiments. Furthermore, the investigation of the demagnetization dynamics of insulators allows one to relate electronic structure to magnetic dynamics.In order to investigate the magnetic dynamics of ferromagnetic insulating BaFeO 3 thin films, we performed time-resolved reflectivity studies at the Femtospex slicing facility at the synchrotron radiation source BESSY II [18], using circularly polarized x-ray pulses. Our experimental method has the advantage that, in one reflectivity experiment, we can probe electronic structure as well as magnetism. BaFeO 2.5 thin films were grown on SrTiO 3 (00...
Using resonant soft-x-ray scattering as a function of both temperature and magnetic field, we reveal a large number of almost degenerate magnetic orders in SrCo 6 O 11 . The Ising-like spins in this frustrated material in fact exhibit a so-called magnetic devil's staircase. It is demonstrated how a magnetic field induces transitions between different microscopic spin configurations, which is responsible for the magnetoresistance of SrCo 6 O 11 . This material therefore constitutes a unique combination of a magnetic devil's staircase and spin-valve effects, yielding a novel type of magnetoresistance system.
We investigated the electronic and magnetic properties of fully oxidized BaFeO3 thin films, which show ferromagnetic-insulating properties with cubic crystal structure, by hard x-ray photoemission spectroscopy (HAXPES), x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). We analyzed the results with configuration-interaction (CI) cluster-model calculations for Fe 4+ , which showed good agreement with the experimental results. We also studied SrFeO3 thin films, which have an Fe 4+ ion helical magnetism in cubic crystal structure, but are metallic at all temperatures. We found that BaFeO3 thin films are insulating with large magnetization (1.7µB /formula unit) under ∼ 1 T, using valence-band HAXPES and Fe 2p XMCD, which is consistent with the previously reported resistivity and magnetization measurements. Although Fe 2p core-level HAXPES and Fe 2p XAS spectra of BaFeO3 and SrFeO3 thin films are quite similar, we compared the insulating BaFeO3 to metallic SrFeO3 thin films with valence-band HAXPES. The CI cluster-model analysis indicates that the ground state of BaFeO3 is dominated by d 5 L (L: ligand hole) configuration due to the negative charge transfer energy, and that the band gap has significant O 2p character. We revealed that the differences of the electronic and magnetic properties between BaFeO3 and SrFeO3 arise from the differences in their lattice constants, through affecting the strength of hybridization and bandwidth.
Ultrafast magnetization reversal of a ferrimagnetic metallic alloy GdFeCo was investigated by time-resolved resonant magneto-optical Kerr effect measurements using a seeded free electron laser. The GdFeCo alloy was pumped by a linearly polarized optical laser pulse, and the following temporal evolution of the magnetization of Fe in GdFeCo was element-selectively traced by a probe free electron laser pulse with a photon energy tuned to the Fe M-edge. The results have been measured using rotating analyzer ellipsometry method and confirmed magnetization switching caused by ultrafast heating.
The relationship between the magnetic interaction and photoinduced dynamics in antiferromagnetic perovskites is investigated in this study. In La1/3Sr2/3FeO3 thin films, commensurate spin ordering is accompanied by charge disproportionation, whereas SrFeO3−δ thin films show incommensurate helical antiferromagnetic spin ordering due to increased ferromagnetic coupling compared to La1/3Sr2/3FeO3. To understand the photoinduced spin dynamics in these materials, we investigate the spin ordering through time-resolved resonant soft x-ray scattering. In La1/3Sr2/3FeO3, ultrafast quenching of the magnetic ordering within 130 fs through a nonthermal process is observed, triggered by charge transfer between the Fe atoms. We compare this to the photoinduced dynamics of the helical magnetic ordering of SrFeO3−δ . We find that the change in the magnetic coupling through optically induced charge transfer can offer an even more efficient channel for spin-order manipulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.