Thiol-capped ZnO nanowire/nanotube arrays with tunable magnetic properties at room temperature.
The present study reports room-temperature ferromagnetic behaviors in three-dimensional (3D)-aligned thiol-capped single-crystalline ZnO nanowire (NW) and nanotube (NT) arrays as well as polycrystalline ZnO NT arrays. Besides the observation of height-dependent saturation magnetization, a much higher M(s) of 166 microemu cm(-2) has been found in NTs compared to NWs (36 microemu cm(-2)) due to larger surface area in ZnO NTs, indicating morphology-dependent magnetic properties in ZnO NW/NT systems. Density functional calculations have revealed that the origin of ferromagnetism is mainly attributed to spin-polarized 3p electrons in S sites and, therefore, has a strong correlation with Zn-S bond anisotropy. The preferential magnetization direction of both single-crystalline NTs and NWs lies perpendicular to the tube/wire axis due to the aligned high anisotropy orientation of the Zn-S bonds on the lateral (100) face of ZnO NWs and NTs. Polycrystalline ZnO NTs, however, exhibit a preferential magnetization direction parallel to the tube axis which is ascribed to shape anisotropy dominating the magnetic response. Our results demonstrate the interplay of morphology, dimensions, and crystallinity on spin alignment and magnetic anisotropy in a 3D semiconductor nanosystem with interfacial magnetism.
Deng
Su-Zi
SZ
Department of Chemistry, National University of Singapore, Singapore.
Fan
Hai-Ming
HM
Wang
Miao
M
Zheng
Min-Rui
MR
Yi
Jia-Bao
JB
Wu
Rong-Qin
RQ
Tan
Hui-Ru
HR
Sow
Chorng-Haur
CH
Ding
Jun
J
Feng
Yuan-Ping
YP
Loh
Kian-Ping
KP
D008280:Magnetics; D008958:Models, Molecular; D008968:Molecular Conformation; D043942:Nanotubes / Q000737:chemistry*; D053770:Nanowires / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013696:Temperature; D015034:Zinc Oxide / Q000737:chemistry*
D013438:Sulfhydryl Compounds; D015034:Zinc Oxide