We have engineered an antiferromagnetic domain wall by utilizing a magnetic frustration effect of a thin iron cap layer deposited on a chromium film. Through lithography and wet etching we selectively remove areas of the Fe cap layer to form a patterned ferromagnetic mask over the Cr film. Removing the Fe locally removes magnetic frustration in user-defined regions of the Cr film. We present x-ray microdiffraction microscopy results confirming the formation of a 90° spin-density wave propagation domain wall in Cr. This domain wall nucleates at the boundary defined by our Fe mask.
We report a comprehensive study on the magnetic and structural properties of the spinel sulfides LiInCr4S8, LiGaCr4S8, and CuInCr4S8, where Li+/Cu+ and Ga3+/In3+ ions form a zinc-blende-type order. On the basis of synchrotron X-ray diffraction and magnetization data obtained using polycrystalline samples, these three sulfides are suggested to be breathing pyrochlore magnets with alternating antiferromagnetic and ferromagnetic interactions on the small and large tetrahedra, respectively. The measured magnetization processes of the three sulfides up to 72 T are significantly different. The magne…
We build a microscopic model to study the intra- and inter-layer superexchange due to electrons hopping in chromium trihalides ($\mathrm{CrX}_3$, X= Cl, Br, and I). In evaluating the superexchange, we identify the relevant intermediate excitations in the hopping. In our study, we find that the intermediate hole-pairs excitations in the $p$-orbitals on X ion play a crucial role in mediating various types of exchange interactions. In particular, the inter-layer antiferromagnetic exchange may be realized by the hole-pair-mediated superexchange. Interestingly, we also find that these virtual hoppi…
The influence of the curvature on the dynamical properties of transversal domain walls in a thin antiferromagnetic wire is studied theoretically. Equations of motion for antiferromagnetic domain wall are obtained within the collective variable approach ($q-Φ$ model). It is shown that (i) for the case of localized bend, curvature results in a pinning potential for domain wall. (ii) The gradient of the curvature results in a driving force on the domain wall and it effectively moves without any external stimuli. Although we showcase our approach on the specific parabola and Euler spiral geometrie…
Understanding of the interaction of antiferromagnetic solitons including domain walls and skyrmions with boundaries of chiral antiferromagnetic slabs is important for the design of prospective antiferromagnetic spintronic devices. Here, we derive the transition from spin lattice to micromagnetic nonlinear $σ$-model with the corresponding boundary conditions for a chiral cubic G-type antiferromagnet and analyze the impact of the slab boundaries and antisymmetric exchange (Dzyaloshinskii--Moriya interaction) on the vector order parameter. We apply this model to evaluate modifications of antiferr…
While magnetic fields generally compete with superconductivity, a type II superconductor can persist to very high fields by confining the field in topological defects, namely vortices. We propose that a similar physics underlies the pseudogap phase in cuprates, where the relevant topological defects are the antiphase domain walls of an underlying antiferromagnetic (AFM) order. A key consequence of this scenario is that the termination of the pseudogap phase should be quantitatively described by the underlying AFM model. We demonstrate that this picture can explain a number of key experimentall…
Magnetic quantum defects in a uniaxial antiferromagnetic insulator
Rutgers University（罗格斯大学）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；National Institute of Chemical Physics and Biophysics（化学物理与生物物理学国立研究所）；University of South Carolina（南卡罗来纳大学）
We have systematically studied the magnetic properties of chromium chalcogene compounds FeCr$_2$Se$_{4-x}$Te$_x$. The FeCr2Se4 undergoes antiferromagnetic ordering below 222 K. Substitution of tellurium lowers the antiferromagnetic ordering temperature and leads to short range ferromagnetic cluster behavior towards the tellurium end. Change over from antiferromagnetic to ferrimagnetic like behavior is also reflected in the corresponding transformation from semiconducting to metallic transport behavior. There is a large variation in the Curie-Weiss temperature, effective magnetic moment and ord…
Spatio-temporal migration of antiferromagnetic domain walls in Sr2IrO4
Department of Physics, University of Colorado at Boulder（科罗拉多大学博尔德分校物理系）；European X-ray Free-Electron Laser Facility（欧洲X射线自由电子激光设施）；Department Physik, Universität Siegen（锡根大学物理系）
Metallic Interface Emerging at Magnetic Domain Wall of Antiferromagnetic Insulator---Fate of Extinct Weyl Electrons
与普通半导体不同，拓扑绝缘体伴随着由狄拉克型费米子描述的受保护的金属表面。在这里，我们从理论上表明，另一个新兴的二维金属嵌入在大块绝缘体实现在磁畴壁。畴壁长期以来一直被研究作为老式和前沿自旋电子学的成分。畴壁在这里，作为一个看似微不足道的反铁磁绝缘体的接口，紧急实现了一个功能接口，由零模式与强大的二维费米表面，其中烧绿石铱氧化物提出主机凝聚态实现外尔费米子提供这样的例子在低温下保存。钉扎在畴壁的inap态的存在，理论上类似于聚乙炔中的自旋/电荷孤子，并作为隐藏的一维弱Chern绝缘体的边缘被保护，其特征在于零维A类拓扑不变量，解决了在R2 Ir 2 O 7中观察到的实验难题。畴壁实现了电子的量子限制，并提供了一个净均匀磁化，这使得磁控制电子界面输运超越半导体范式。
Ferroic domain walls (DWs) create different symmetries and ordered states compared with those in single-domain bulk materials. In particular, the DWs of an antiferromagnet (AFM) with non-coplanar spin structure have a distinct symmetry that cannot be realized in those of their ferromagnet counterparts. In this paper, we show that an unconventional anomalous Hall effect (AHE) can arise from the DWs of a non-coplanar AFM, Nd2Ir2O7. Bulk Nd2Ir2O7 has a cubic symmetry; thus, its Hall signal should be zero without an applied magnetic field. The DWs generated in this material break the two-fold rota…
Anomalous metallic states at magnetic interfaces in an antiferromagnetic topological insulator candidate DyPtBi with ferroquadrupolar order
University of Tokyo（东京大学）；Hiroshima University（广岛大学）；Kobe University（神户大学）；Hokkaido University（北海道大学）；High Energy Accelerator Research Organization（高能加速器研究机构）；RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所涌现物质科学中心）；Tokyo College, University of Tokyo（东京大学东京学院）
We analyze the low-energy dynamics of quasi one dimensional, large-$S$ quantum antiferromagnets with easy-axis anisotropy, using a semi-classical non-linear sigma model. The saddle point approximation leads to a sine Gordon equation which supports soliton solutions. These correspond to the movement of spatially extended domain walls. Long-range magnetic order is a consequence of a weak inter-chain coupling. Below the ordering temperature, the coupling to nearby chains leads to an energy cost associated with the separation of two domain walls. From the kink-antikink two-soliton solution, we com…
We have studied a nearly stoichiometric insulating Y$_{0.97(2)}$Cr$_{0.98(2)}$O$_{3.00(2)}$ single crystal by performing measurements of magnetization, heat capacity, and neutron diffraction. Albeit that the YCrO$_3$ compound behaviors like a soft ferromagnet with a coersive force of $\sim$ 0.05 T, there exist strong antiferromagnetic (AFM) interactions between Cr$^{3+}$ spins due to a strongly negative paramagnetic Curie-Weiss temperature, i.e., -433.2(6) K. The coexistence of ferromagnetism and antiferromagnetism may indicate a canted AFM structure. The AFM phase transition occurs at $T_\tex…
We search for dynamical magnetoelectric phenomena in three-dimensional correlated systems with spin-orbit coupling. We focus on the antiferromagnetic insulator phases where the dynamical axion field is realized by the fluctuation of the antiferromagnetic order parameter. It is shown that the dynamical chiral magnetic effect, an alternating current generation by magnetic fields, emerges due to the time dependences of the order parameter such as antiferromagnetic resonance. It is also shown that the anomalous Hall effect arises due to the spatial variations of the order parameter such as antifer…
Topological magnetic Weyl semimetals have been proposed to host controllable chiral domain walls which bear a great prospect in device applications. To exploit them in applications, it is important to have a proper way to tune and manipulate these domain walls. One possible means is through magnetoelastic coupling. The involvement of rare earth in the lately proposed $R$Al$X$ ($R$=rare earth, $X$=Si and Ge) family magnetic Weyl semimetals may provide such a platform. Here we present transport and thermodynamic properties of CeAlGe under hydrostatic pressure. We find that pressure enhances the …
Comment on ``Magnetoresistance Anomalies in Antiferromagnetic YBa$_2$Cu$_3$O$_{6+x}$: Fingerprints of Charged Stripes''
在最近的一封信中，Ando等人（cond-mat/9905071）在空穴掺杂的反铁磁YBa $_2$ Cu $_3$ O $_{6+x}$中发现了异常磁阻（MR），他们将其归因于带电条纹，即，将孔分离成线。在这篇评论中，我们表明，这些实验虽然有趣，但并不能证明条纹的存在。在我们看来，异常行为是由于（a，b）平面的电阻率的各向异性在散装和磁场相关的反铁磁（AF）域结构。畴壁不太可能是带电的条纹。
