TY - JOUR
T1 - Competing magnetic interactions and interfacial frozen-spins in Ni-NiO core-shell nano-rods
AU - Hsu, Hao Chun
AU - Lo, Chih Chieh
AU - Tseng, Yuan-Chieh
PY - 2012/3/15
Y1 - 2012/3/15
N2 - This paper investigates the subtle interfacial magnetism of highly-aligned, free-standing Ni-NiO core-shell rods on a Si substrate, fabricated by electroless-plating and an anodic aluminum oxide template. Transmission electron microscopy found that the NiO shell was uniformly present along the entire rod. Vertical magnetization shift, arising from opposite field cooling conditions, suggests frozen spins (FS) at the Ni-NiO interface. The FS were related to the pinning effects of the NiO on the Ni. The pinning strength depended on the NiO thickness, displaying a tunable fashion from 6 to 10 nano-meters with thermal annealing. The FS mediated the antiferromagnetic (AFM)-ferromagnetic (FM) interfacial coupling, leading to the temperature-dependent properties of the rods. FS were evident below 100 K, at which the NiO-AFM dominated the properties with a suppressed coercive field and non-saturated magnetization. At 100 K, however, the Ni-FM was superior to the NiO-AFM with a restored FM phase. Meanwhile, the interfacial magnetic frustration occurred due to the disappearance of FS. These two factors resulted in the coercivity enhancement at 100 K. The uniqueness of the structure opens opportunities to tailoring the properties of the rods by manipulating the core-shell inter-dependency, as well as inspiring further researches concerning its applications in spintronics.
AB - This paper investigates the subtle interfacial magnetism of highly-aligned, free-standing Ni-NiO core-shell rods on a Si substrate, fabricated by electroless-plating and an anodic aluminum oxide template. Transmission electron microscopy found that the NiO shell was uniformly present along the entire rod. Vertical magnetization shift, arising from opposite field cooling conditions, suggests frozen spins (FS) at the Ni-NiO interface. The FS were related to the pinning effects of the NiO on the Ni. The pinning strength depended on the NiO thickness, displaying a tunable fashion from 6 to 10 nano-meters with thermal annealing. The FS mediated the antiferromagnetic (AFM)-ferromagnetic (FM) interfacial coupling, leading to the temperature-dependent properties of the rods. FS were evident below 100 K, at which the NiO-AFM dominated the properties with a suppressed coercive field and non-saturated magnetization. At 100 K, however, the Ni-FM was superior to the NiO-AFM with a restored FM phase. Meanwhile, the interfacial magnetic frustration occurred due to the disappearance of FS. These two factors resulted in the coercivity enhancement at 100 K. The uniqueness of the structure opens opportunities to tailoring the properties of the rods by manipulating the core-shell inter-dependency, as well as inspiring further researches concerning its applications in spintronics.
UR - http://www.scopus.com/inward/record.url?scp=84859555682&partnerID=8YFLogxK
U2 - 10.1063/1.3699039
DO - 10.1063/1.3699039
M3 - Article
AN - SCOPUS:84859555682
VL - 111
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 6
M1 - 063919
ER -