All-in-all-out magnetic domain wall conduction in a pyrochlore iridate heterointerface

Editors' Suggestion

All-in-all-out magnetic domain wall conduction in a pyrochlore iridate heterointerface

T. C. Fujita, M. Uchida, Y. Kozuka, W. Sano, A. Tsukazaki, T. Arima, and M. Kawasaki

Phys. Rev. B 93, 064419 – Published 17 February 2016

Abstract

Pyrochlore oxides possessing “all-in-all-out” spin ordering have attracted burgeoning interest as a rich ground of emergent states. This ordering has two distinct types of magnetic domains (all-in-all-out or all-out-all-in) with broken time-reversal symmetry, and a nontrivial metallic surface state has been theoretically demonstrated to appear at their domain wall. Here, we report on the observation of this metallic conduction at the single all-in-all-out/all-out-all-in magnetic domain wall formed at the heterointerface of two pyrochlore iridates. By utilizing the different magnetoresponses of them with different lanthanide ions, the domain wall is controllably inserted at the heterointerface, the surface state being detected as an anomalous conduction enhancement with a ferroic hysteresis. Our establishment paves the way for further investigation and manipulation of this new type of surface transport.

Received 9 November 2015
Revised 1 February 2016

DOI:https://doi.org/10.1103/PhysRevB.93.064419

Physics Subject Headings (PhySH)

Domain walls Magnetoresistance

Heterostructures Interfaces Oxides Pyrochlores

Transport techniques

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

T. C. Fujita¹, M. Uchida^1,*, Y. Kozuka¹, W. Sano¹, A. Tsukazaki^1,2,3, T. Arima^4,5, and M. Kawasaki^1,5

¹Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
²Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
³PRESTO, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
⁴Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan
⁵RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan

^*uchida@ap.t.u-tokyo.ac.jp

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 93, Iss. 6 — 1 February 2016

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Two distinct all-in-all-out spin structures, named the A (all-in-all-out) domain and the B (all-out-all-in) domain, on a pyrochlore lattice. (b) and (c) Their eigenstates near the Fermi level ( $E_{F}$ ) have different phase factors (±ϕ), and they are switched by time-reversal operation, leading to the surface state at the domain wall accompanied with ferromagnetic moments indicated by open green arrows. (d) Cross-sectional schematics of the heterostructure composed of $E u_{2} I r_{2} O_{7}$ (EIO) with $J = 0$ nonmagnetic $E u^{3 +}$ and $T b_{2} I r_{2} O_{7}$ (TIO) with $J = 6$ Ising-like $T b^{3 +}$ , which are used as the “pinned layer” and the “free layer” and controlled by $B_{cool}$ and $B_{sweep}$ , respectively. Their magnetic domain structures are changed depending on $B_{cool}$ and $B_{sweep}$ . Domain wall conduction paths (denoted by yellow lines) emerge when the domain structure is opposite in the EIO and TIO layers.
Reuse & Permissions
Figure 2
(a) θ-2θ scan of x-ray diffraction. Peaks from the YSZ substrate are marked with asterisks. The magnified view around YSZ (222) is shown in (b). (c) Reciprocal space mapping around the YSZ (331) peak. An ideal pyrochlore lattice with cubic symmetry follows the dashed line. (d) Phase contrast image of high-resolution TEM of the EIO/TIO heterostructure on the YSZ (111) substrate. (e) Integrated intensity along the [111] direction of the energy dispersive x-ray spectrometry (EDX) for Eu and Tb. (f) Magnified high-angle annular dark field scanning transmission electron microscope image and cross-sectional EDX mappings for Eu, Tb, and Ir elements.
Reuse & Permissions
Figure 3
(a) Temperature dependence of the longitudinal resistivity ( $ρ_{xx}$ ) for 15-nm EIO and 60-nm TIO thin films. The magnetic transition temperature $T_{N}$ is indicated by the dashed line. (b) and (c) Sweeping magnetic field ( $B_{sweep}$ ) dependence of longitudinal conductance $G_{xx}$ for (b) EIO and (c) TIO measured at 10 K. The magnetic domain structure of EIO is determined by cooling field ( $B_{cool}$ ), whereas that of TIO can be switched by $B_{sweep}$ . The direction of the hysteresis originating from domain switching is shown by arrows where open (filled) and red (blue) ones correspond to the domain structure for the A (B) domain.
Reuse & Permissions
Figure 4
(a)–(c) Sweeping magnetic field ( $B_{sweep}$ ) dependence of longitudinal conductance $G_{xx}$ for an EIO/TIO heterostructure measured at 10 K after various cooling field ( $B_{cool}$ ) conditions. The line colors indicate the magnetic domain structure in the TIO layer [red (blue) for the A (B) domain]. The direction of hysteresis is shown by arrows, whose colors also indicate the magnetic domain structure in the TIO layer. (d) and (e) $B_{sweep}$ dependence of the subtracted conductance defined by $G_{xx} (\pm 9 T FC) - G_{xx} (ZFC)$ for the heterostructure. These results correspond to the summation of linear magnetoconductance in the EIO layer and additional conductance at the interface ( $G_{int}$ ). (f) $B_{sweep}$ dependence of the linear magnetoconductance (upper half) and $G_{int}$ (lower half) resolved from (d) and (e).
Reuse & Permissions
Figure 5
(a) and (b) Temperature dependence of the interfacial conductance ( $G_{int}$ ), compared with that of the total longitudinal conductance $G_{xx}$ of the EIO/TIO heterostructure. The magnetic transition temperature $T_{N}$ is estimated to be about 105 K from the peak in the temperature derivative.
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics