Periodic chiral magnetic domains in single-crystal nickel nanowires

Journal Article · Mon Jun 18 00:00:00 EDT 2018 · Physical Review Materials

DOI:https://doi.org/10.1103/PhysRevMaterials.2.064406· OSTI ID:1489659

Kan, Jimmy J. ^[1]; Lubarda, Marko V. ^[2]; Chan, Keith T. ^[1]; Uhlíř, Vojtěch ^[3]; Scholl, Andreas ^[4]; Lomakin, Vitaliy ^[1]; Fullerton, Eric E. ^[1]

---

1. Univ. of California, San Diego, CA (United States). Center for Memory and Recording Research
2. Univ. of California, San Diego, CA (United States). Center for Memory and Recording Research; Univ. of Donja Gorica, Podgorica (Montenegro). Faculty of Polytechnics
3. Brno Univ. of Technology (Czech Republic)
4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source

We report here on experimental and computational investigations of the domain structure of single-crystal Ni nanowires (NWs). The $${\sim}200\times{}200\times{}8000\mathrm{n}{\mathrm{m}}^{3}$$ Ni NWs were grown by a thermal chemical vapor deposition technique that results in single-crystal structures. Magnetoresistance measurements of individual NWs suggest the average magnetization points largely off the NW long axis at zero field. X-ray photoemission electron microscopy images obtained at room temperature show a well-defined periodic magnetization pattern along the surface of the nanowires with a period of $${{\lambda}}_{\mathrm{avg}}=239\pm{}37\mathrm{nm}$$. Finite element micromagnetic simulations reveal that when the material parameters of the modeled system match those of nickel crystal at $$T=10\mathrm{K}$$, an oscillatory magnetization configuration with a period closely matching experimental observation ($${\lambda}=222\mathrm{nm}$$) is obtainable at remanence. This magnetization configuration involves a periodic array of alternating chirality vortex domains distributed along the length of the NW. Vortex formation is attributable to the relatively high cubic anisotropy of the single crystal Ni NW system at $$T=10\mathrm{K}$$ and its reduced structural dimensions. The periodic alternating chirality vortex state is a topologically protected metastable state, analogous to an array of 360° domain walls in a thin strip. Simulations show that other remanent states are also possible, depending on the field history. At room temperature ($$T=273\mathrm{K}$$), simulations show vortices are no longer stable due to the expected reduced cubic anisotropy of the system, suggesting a disparity between the fabricated and modeled nanowires. Negative uniaxial anisotropy and magnetoelastic effects in the presence of compressive biaxial strain are shown to promote and restore formation of vortices at room temperature.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Science Foundation (NSF)
• Grant/Contract Number: AC02-05CH11231; DMR-0906957
• OSTI ID: 1489659
• Alternate ID(s): OSTI ID: 1454662
• Journal Information: Physical Review Materials, Vol. 2, Issue 6; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
domain walls
ferromagnetism
growth
magnetic anisotropy
magnetic texture