We report experimental observations of chiral magnetic skyrmion phases in thin films of molybdenum nitride with a filled β-Mn-type structure. A series of Fe2−xPdxMo3N (x = 0.15, 0.32, and 0.54) thin films are grown epitaxially with the (110) orientation on c-plane sapphire substrates by reactive magnetron sputtering, and their structural, magnetic, and transport properties are investigated. Studies using the Topological Hall effect and Lorenz transmission electron microscopy imaging for films with x = 0.32 identified the existence of two types of skyrmion phases with a size as small as 60 nm; one is a dense skyrmion phase at temperatures below 100 K, and the other is an isolated skyrmion phase in a higher temperature range to well beyond room temperature. These epitaxial thin films in the family of molybdenum nitrides open the way for the study of skyrmions, manipulation of their properties, and the exploration and optimization for skyrmion-based applications.
The magnetic phase diagram and topological Hall effect (THE) are studied by magnetization and transport measurements for chiral antiferromagnet (AFM) Co2-xPdxMo3N (x = 0-1.61) thin films with the filled β-Mn-type chiral structure, which reveals the rich phase diagram in the temperature versus Pd content x plane, where a collinear AFM, a canted AFM, and a low-temperature phase below about 50 K are found to exist. For thin films with x = 1.01〜1.61, the low-temperature phase shows prominent THE. The formation of the canted AFM phase with the Néel temperature up to 325 K is observed with vanishing THE. These findings establish the chiral antiferromagnetic molybdenum nitrides as a fertile playground for exploring the interplay between chiral antiferromagnetism, topological spin textures, and novel magnetotransport phenomena.
Hall transport and non-collinear magnetoresistance (NCMR) are studied for a chiral antiferromagnet (AFM) with the filled β-Mn-type structure. Magnetic and transport properties of epitaxial thin films of Co2−xPdxMo3N revealed that, in addition to a canted antiferromagnetic behavior above room temperature, thin films with x = 1.01∼1.38 exhibited a transition to a spin spiral state with a higher magnetic moment below TSR of around 50 K, which was assigned to a spin reorientation transition. The low-temperature phase shows both large anomalous Hall effect (AHE) and topological Hall effect (THE). Upon the transition to the canted AFM phase existing up to room temperature, the large AHE still persists with vanishing THE. The behavior of the Hall transport properties coupled with NCMR signals in the current-perpendicular-to-the plane configuration shows the formation of topological spin textures with locally antiferromagnetic order. The present results open the way for the study of topological antiferromagnetic spin textures, manipulation of their properties, and for future spintronic applications.
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