Photoinduced sign inversion of the anomalous Hall effect in EuO thin films

Ohuchi, Yuki; Kozuka, Y.; Rezaei, Nafise; Bahramy, M. S.; Arita, Ryotaro; Ueno, Kazunori; Tsukazaki, Atsushi; Kawasaki, Masashi

doi:10.1103/physrevb.89.121114

Cited by 8 publications

(4 citation statements)

References 37 publications

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“…The classical ferromagnetic semiconductor EuO [118,119] is one of the leading candidates hosting skyrmionic structures. As shown in figure 6(a), topological Hall resistivity ρ THE has been observed as a sharp peak in the magnetization process in EuO, in addition to the conventional anomalous Hall resistivity ρ AHE proportional to magnetization [120][121][122]. The ρ THE peak appears only in films thinner than t = 200 nm.…”

Section: Topological Spin Structures In Oxide Filmsmentioning

confidence: 87%

Topological properties and functionalities in oxide thin films and interfaces

Uchida

Kawasaki

2018

J. Phys. D: Appl. Phys.

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As symbolized by the Nobel Prize in Physics 2016, "topology" has been recognized as an essential standpoint to understand and control the physics of condensed matter. This concept may be spreading even into application areas such as novel electronics. In this trend, there has been reported a number of study for the oxide films and heterostructures with topologically non-trivial electronic or magnetic states. In this review, we overview the trends of new topological properties and functionalities in oxide materials with sorting out a number of examples. The technological advances in oxide film growth achieved over the last few decades are now opening the door for harnessing novel topological properties. two-dimensional chiral p-wave superconductivity, a topological superconducting state equivalent to the Pfaffian state, the Majorana zero modes are expected to localize in vortex cores. Their non-abelian braiding has also attracted recent interest due to its possible application to the topological quantum computation. 2-2. Properties and functionalities of topological spin structuresA striking example of the topologically non-trivial spin structure is magnetic skyrmion [21]. In a typical structure called Bloch-type skyrmion, spins in two dimensions gradually rotate towards the center in perpendicular to the radius directions, as illustrated in Fig. 1(b) [22,23]. The topological invariant concerned is integer skyrmion number (0, ±1, ±2, ...), defined as integral of solid angle subtended by constituent spins in real space. The single skyrmion behaves as a topologically protected spin object, thus attracting rising attention as a robust information carrier in solids. Here, for stabilizing canting of neighboring spins, asymmetric Dzyaloshinskii-Moriya (DM) interaction derived from the spin-orbit coupling is a key parameter. The skyrmion and its lattice structure have been directly observed in chiral metals such as B20type transition-metal silicides and germanides [22,24] and a chiral insulator [25] by some special transmission electron microscopy techniques.Recent studies show promise for the application of the skyrmion to non-volatile magnetic memory, which has the advantages of low driving current and high memory density over the magnetic bubble and racetrack memory devices [26,27]. The non-coplanar spin alignment in the skyrmion produces emergent magnetic field to conduction electrons, resulting in giant Hall effect that is already applied for detecting the skyrmions [28][29][30][31][32][33]. Lately, in addition to the Bloch-type skyrmion, more variety of topological spin structures have been discovered such as Néel-type skyrmion [34,35] and anti-skyrmion [36,37]. More effort will focus on engineering skyrmionic materials in order to realize stable manipulation of skyrmions above room temperature. 3-1. Topological electronic states in oxide filmsCompared to selenides and tellurides forming a group of topological insulator materials, reports of threedimensional topological insulator in oxides have been limited to theo...

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Section: Topological Spin Structures In Oxide Filmsmentioning

confidence: 87%

Topological properties and functionalities in oxide thin films and interfaces

Uchida

Kawasaki

2018

J. Phys. D: Appl. Phys.

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“…AHE is known to increase with carrier concentration (n) [27]. Photoionization experiments, elevating n to about 4 • 10 19 cm −3 (30% increase) [31], indeed change the anomalous Hall conductivity σ AH from 0.2 S•cm −1 to about 1 S•cm −1 . Remarkably, at a critical value of longitudinal conductivity σ xx ≈ 100 S•cm −1 , σ AH reverses its sign from negative to positive with respect to magnetic field.…”

Section: Introductionmentioning

confidence: 93%

“…It is suggested [33] that carrier concentrations in EuO exceeding 5 • 10 −19 cm −3 can be reached only by chemical doping with rare-earth trivalent metals. Also, oxygen-deficient EuO employed in AHE experiments [30][31][32][33] is synthesized using pulsed laser deposition-a technique that can hardly control dopant incorporation-leading to an uncontrolled amount and distribution of defects. Here we report the successful synthesis of Gd-doped EuO epitaxial films within heterostructures SiO/Eu 1−x Gd x O/ EuO/Si employing the full potential of molecular beam epitaxy to control the doping.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Hall effect in the prospective spintronic material Eu_1−xGd_xO integrated with Si

Parfenov

Averyanov²,

Tokmachev³

et al. 2016

J. Phys.: Condens. Matter

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Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm(-1) in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies.

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“…The interest in EuO has seen a considerable upswing recently due to its potential as a spintronics material. For example, EuO devices were employed to for spin filtering [9][10][11][12], the interface between EuO and GdN is expected to produce a band inversion and a nonzero Chern number [13], a giant spin-phonon coupling has been reported [14], it has been suggested that a CdO/EuO superlattice is a Weyl semimetal [15], and the Hall effect of EuO thin films has been observed [16,17]. Efforts to increase the Curie temperature via doping and alloying of EuO have also seen a resurgency: Curie temperatures up to 134 K in single crystals and even higher in thin films have been achieved [18][19][20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Growth of EuO single crystals at reduced temperatures

et al. 2017

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Single crystals of (Eu1-xBax)O have been grown in a molten barium-magnesium metal flux at temperatures up to 1000°C, producing single crystals of (Eu1-xBax)O with barium doping levels ranging from x=0.03 to x=0.25. Magnetic measurements show that the ferromagnetic Curie temperature TC correlates with the Ba doping levels, and a modified Heisenberg model was used to describe the stoichiometry dependence of TC. Extrapolation of the results indicates that a sample with Ba concentration of x=0.72 should have a TC of 0 K, potentially producing a quantum phase transition in this material.

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Photoinduced sign inversion of the anomalous Hall effect in EuO thin films

Cited by 8 publications

References 37 publications

Topological properties and functionalities in oxide thin films and interfaces

Topological properties and functionalities in oxide thin films and interfaces

Anomalous Hall effect in the prospective spintronic material Eu_1−xGd_xO integrated with Si

Growth of EuO single crystals at reduced temperatures

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Photoinduced sign inversion of the anomalous Hall effect in EuO thin films

Cited by 8 publications

References 37 publications

Topological properties and functionalities in oxide thin films and interfaces

Topological properties and functionalities in oxide thin films and interfaces

Anomalous Hall effect in the prospective spintronic material Eu1−xGdxO integrated with Si

Growth of EuO single crystals at reduced temperatures

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About

Anomalous Hall effect in the prospective spintronic material Eu_1−xGd_xO integrated with Si