Study of spin-switching by meansot superconductor-ferromagnet junction

铁磁体(F)/超导体(S)/铁磁体(F)结在两个铁磁层磁自旋的平行耦合(P)和反平行耦合（AP）之间，理论上预计具有不同的超导临界温度（Tc），即在很小的磁场变化下，电阻率可能发生巨大变化。这种新型结在低驱动磁场下具有高信噪比的新型开关传感器中具有实际应用前景。为了研究上述Tc差异的可能性，我们在(1)S/N（正常金属）、(2)S/F和(3)AF（反铁磁体）/F/S/F等多层体系的基本超导特性之外，进行了Tc测量，这是开发新材料所必需的。系统(1)和(2)的测量结果明确了Tc和Hc2等基本超导性质。特别是我们发现了S/F三层和五层之间不同的振荡行为，反映了超导对函数的ο相和π相。对系统(3)的测量结果表明，通过选择f层厚度的可用尺寸，磁化测量揭示了f层随外加磁场的平行和反平行耦合。然而，即使选择最佳的Slayer厚度尺寸，伴随平行和反平行磁耦合的Tc差异也很小。

Ferromagnet(F)/Superconductor(S)/Ferromagnet(F) junction is theoretically expected to have different superconducting critical temperature(Tc) between parallel(P) and antiparallel(AP) coupling of the magnetic spins of both the ferromagnetic layers, that is huge change in electrical resistivity will be possible under the change in small magnetic field. This new junction is prospected to the practical use for the novel switching sensor having high S/N ratio under low driving magnetic field. In order to investigate the possibility above mentioned Tc-difference, we have done the Tc measurement in addition to the basic superconducting properties, which is necessary for the exploitation of new material, for the several multilayer systems, such as (1) S/N(normal metal), (2) S/F and (3) AF(antiferromagnet)/F/S/F. The results of the measurement for the systems (1) and (2) make clear the basic superconducting properties such as Tc and Hc2. Especially we have found the different oscillation behavior between S/F tri- and penta-layers reflecting the ο- and π- phases of superconducting pair funcfion. The result of the measurement for system (3) shows that, by means of selecting available size of F-layer's thickness, the magnetization measurement reveals the parallel and antiparallel coupling of both F-layers depending on the applied magnetic field. The difference in Tc accompanied by the parallel and antiparallel magnetic coupling, however, is very small even selecting optimum size of Slayer thickness.