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Chen, Y.*; 塩見 雄毅*; Qiu, Z.*; 新関 友彦*; 埋田 真樹*; 齊藤 英治
Scientific Reports (Internet), 9, p.19052_1 - 19052_8, 2019/12
被引用回数：0 パーセンタイル：0(Multidisciplinary Sciences)In superconductors, a topological configuration of the superconducting order parameter called a superconducting vortex carries magnetization. Such a magnetic topological object behaves like a minute particle generating a magnetic flux. Since the flux is localized with a nanometer scale, the vortex provides a nano-scale probe for local magnetic fields. Here we show that information of magnetic stripes in insulators can be read out by using vortices in an adjacent superconductor film as a probe. The orientation and width of magnetic micro stripes are both transcribed into resistance change of the superconductor through the modulation of vortex mobility affected by local magnetization. By changing the direction of external magnetic fields, zero-field resistance changes continuously according to the stripe orientation, and its modulation magnitude reaches up to 100%. The width of the stripes can also be estimated from the oscillatory magnetoresistance. Our results demonstrate a new possibility for non-volatile analog memory devices based on topological objects.
-Fe
O
/NiO/Pt epitaxial stacksDong, B.-W.*; Baldrati, L.*; Schneider, C.*; 新関 友彦*; Ramos, R.*; Ross, A.*; Cramer, J.*; 齊藤 英治; Kl
ui, M.*
Applied Physics Letters, 114(10), p.102405_1 - 102405_5, 2019/03
被引用回数：11 パーセンタイル：49.82(Physics, Applied)We study the spin Hall magnetoresistance (SMR) in epitaxial -FeO/NiO(001)/Pt stacks, as a function of temperature and thickness of the antiferromagnetic insulating NiO layer. Upon increasing the thickness of NiO from 0 nm to 10 nm, we detect a sign change of the SMR in the temperature range between 10 K and 280 K. This temperature dependence of the SMR in our stacks is different compared to that of previously studied yttrium iron garnet/NiO/Pt, as we do not find any peak or sign change as a function of temperature. We explain our data by a combination of spin current reflection from both the NiO/Pt and -FeO/NiO interfaces and the thickness-dependent exchange coupling mode between the NiO and -FeO layers, comprising parallel alignment for thin NiO and perpendicular alignment for thick NiO.
新関 智彦*; 吉川 貴史*; 内田 健一*; 岡 美嶺人*; 鈴木 和也*; 柳原 英人*; 喜多 英治*; 齊藤 英治
AIP Advances (Internet), 5(5), p.053603_1 - 053603_6, 2015/05
被引用回数：39 パーセンタイル：81.57(Nanoscience & Nanotechnology)The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. Externalmagnetic-field (
) dependence of the LSSE voltage (
) in the Pt/CFO(110) sample with ![$$H |[001]$$](/search/images/ERECAXD2LMYDAMK3EQ.gif)
was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with ![$$H |[1 overline{1} 0]$$](/search/images/ERECAXD2LMYSAXDPOZSXE1DJNZSXWML3EAYF0JA.gif)
shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of has a linear relationship with the temperature difference (
), giving the relatively large / of about 3 
V/K for CFO(110) which was kept even at zero external field.
