| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1997: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
In general, random magnets show multiform properties depending on time- and space-scales of observation. In this project, we investigated spin-glass(SG) systems, cluster-glass(CG) systems and competing anisotropy systems by observing the following quantities (1) low-field dc-magnetization, (2) magnetization up to high-field region, (3) ac-susceptibility, (4) neutron magnetic scattering and (5) muSR spectra, each of which was measured by using methods with different time- and space-scales of observation. Below, we summarize the main results. [A] SG and CG systems (I) On the SG system Fe_xMn_<1-x>TiO_3, we measured long-time relaxations of zero-field-cooled magnetization M_<ZFC> in the M_<ZFC>-T plane(H=const) and the M_< ZFC >-H plane(T=const) for a certain time tw and after tw we increased T(or H). The response of M_<ZFC> for the increase of T(or H) indicates that M_<ZFC> is a function of (T,H). This seems inconsistent with the existence of the long-time relaxation of M_<ZFC> at a cons
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tant T and H.However, we consider that these facts reflect the multiform sides of the complicated properties of SG systems. (2) When the value of M_<ZFC>(T,H) is the same even if M_<ZFC>(T,H) is reached by the different process, the relaxation of M_<ZFC>(T,H) proceeds similarly. We infer that tills phenomenon is common in SG(CG) systems. (3) In the magnetization process of M_<ZFC>, when the sweep-rate of H is larger than the critical value, M_<ZFC> jumps to the field-cooled value M_<FC>, which is explained by the hierarchical organization model with multi-valey structures. (4) From the examination of the effects of the T-cycle and the H-cycle on the relaxation phenomenon of magnetizations for the CG system Fe_xMg_<1-x>TiO_3, the CG system is suggested to be explained also by the hierarchical organization model. (5) The muSR measurement has clarified that the critical region of CG system around the freezing temperature Tf is much wider than that of SG system, which is due to the formation of magnetic clusters at temperatures much higher than Tf. [B] In the competing anisotropy system Fe_xCo_<1-x>TiO_3, the occurrence of the spin-flop transition accompanied with the elongation and the reduction of the transverse spin component and the longitudinal one was firstly shown. This indicates that the orthogonal spin components are coupled. Less
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