Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls

Abstract

Magnetotransport measurements on small single crystals of Cr, the elemental antiferromagnet, reveal the hysteretic thermodynamics of the domain structure. The temperature dependence of the transport coefficients is directly correlated with the real-space evolution of the domain configuration as recorded by x-ray microprobe imaging, revealing the effect of antiferromagnetic domain walls on electron transport. A single antiferromagnetic domain wall interface resistance is deduced to be of order 5 10 ÿ5 cm 2 at a temperature of 100 K. DOI: 10.1103/PhysRevLett.98.117206 PACS numbers: 75.50.Ee, 72.20.My, 73.90.+f, 75.60.Ch Magnetic domains constitute the internal architecture of a host of technologically interesting materials. How ferromagnetic domains form, move, and scatter electrons lies at the heart of items from electrical motors and transformers to data storage devices [1]. In an ordinary ferromagnet (FM), a domain is characterized by a single vector, namely, its magnetization. Antiferromagnets (AF) typically are characterized by multiple vectors corresponding to the local magnetization and how it evolves with position, and offer new and expanded microscopic architectures for exploitation. However, with neither a net magnetic moment nor long wavelength features, antiferromagnetic domains have resisted the detailed characterization that underpins the applications prevalent for ferromagnetic domains.The field has grown in recent years, with an increasing number of studies focused on antiferromagnetic domain imaging [2 -4] and an improved understanding of the microscopic details of the exchange-bias effect in magnetic microstructures [2]. Despite this progress, little attention has been devoted to the transport properties of AF domains and domain walls themselves. As the ability to craft device features progresses to ever smaller dimensions, and hybrid devices mixing ferromagnetic and antiferromagnetic components proliferate, the need to understand the effects on transport of antiferromagnetic domain structure on the microscale, and domain walls on the nanoscale, becomes increasingly acute.We present here a combined electrical transport and x-ray microprobe imaging study of a model AF. We show that magnetotransport measurements on small single crystals of Cr, the elemental spin-density-wave AF, are highly sensitive to the domain structure, and we directly correlate the temperature-dependent and hysteretic behavior of the transport coefficients with the real-space evolution of the domain structure. Combining the x-ray images with the measured anisotropic resistivity yields a quantitative estimate of the electrical resistance of a single antiferromagnetic domain wall.The incommensurate spin-density wave (SDW) in chromium is an antiferromagnetic state that is caused by a nesting instability of the paramagnetic Fermi surface [5,6]. The SDW modulation vector Q is selected by the nesting condition and may lie along any of the cubic crystallographic axes, leading to so-called ''Q domains.'' Between the Néel ordering...

Nanoscale mechanics of antiferromagnetic domain walls

“…While the focus of these advances has been on directly controlling and reading the bulk Néel vector of antiferromagnets [8] and their domains [9], the study and direct control of individual antiferromagnetic DWs has received much less attention thus far. Domain walls, however, are of particular relevance to the field, as they carry essential information on the magnetic microstructure of a material [10,11], can have fundamentally different properties from the interior of domains [12,13], and delimit logical bits in magnetic memory devices [14]. Furthermore, and akin to ferromagnet-based DW logic [15,16], the understanding and control of antiferromagnetic DWs could inform novel approaches to antiferromagnetic spintronics architectures.…”

Magnetism and superconductivity driven by identical 4 f states in a heavy-fermion metal

“…Further reducing the magnetic field and inside the superconducting state the second domain successively becomes populated balancing the domain population when reaching B = 0, identical to the zfc case. The associated domain walls strongly influence the magnetotransport only if the electronic mean free path ℓ is comparable to or larger than the domain wall thickness δ [15]. The lack of hysteresis in our transport measurements suggests that this criterion is not met in the B ⊥ c direction, i.e., δ ≫ ℓ.…”

Phase coexistence and pinning of charge density waves by interfaces in chromium

“…In thin-films grown along the [001] direction the SDW/CDW usually has the wave vector pointing normal to the film surface with spins lying in the film plane [7,10]. The SDW/CDW period is quantized due to confined geometry and follows a thermal hysteresis [8,[11][12][13]. Pinning of the SDW and CDW in Cr by impurities was studied theoretically [14,15] and experimentally [16].…”