| Budget Amount *help |
¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 1994: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1993: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1992: ¥4,900,000 (Direct Cost: ¥4,900,000)
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| Research Abstract |
We have considered that, in order to extract multiform properties of spin-glass (SG) systems, a combined application of various techniques with different time-and space-scale of observation is useful. In this project, we investigated five short-range SG systems (see below) using the following techniques : (1) low-de-field magnetization, (2) ac-susceptibility, (3) Mossbauer spectra, (4) neutron scattering, (5) muSR,and(6) magnetization process up to high-field region. The samples examined are as follows. (A) Magnetically non-diluted system : typical Ising system Fe_xMn_<1-x>TiO_3, and Heisenberg-like system Ni_xMn_<1-x>TiO_3. (B) Diluted systems : Ising systems Fe_xZn_<1-x>F_2 and Fe_xMg_<1-x>TiO_3, and Heisenberg-like system Mn_xMg_<1-x>TiO_3. The followings are summary of our results. (1) Fe_xMn_<1-x>TiO_3 : (1) Details of x-T magnetic phase diagram was decided. (2) Experimental supports for de-Almeida-Thouless theory were given. (3) We found the phenomena consistent with the consider
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ation that the spin state reached under field-cooled conditions is stable, and the spin system forms a hierarchical organization with many valley structures. (4) Below SG-freezing temperature (TSG) , fluctuations of spins remain, which is attributed to the existence of the transverse spin component (5) The reentrant transition was suggested to be a phase transition by observing the divergent behavior of non-linear susceptibility. (2) Ni_xMn_<1-x>TiO_3 : We firstly observed with experiments that the orthogonal spin components in a Heisenberg-like system with weak spin anisotropy freeze succesively at different temperatures (x=0.42,0.47) . (3) Fe_<0.26>Zn_<0.74>F_2 and Fe_<0.2>Mg_<0.8>TiO_3 : SG-freezing was shown to occur among AF-clusters which were formed at temperatures higher than 2T_<SG>. Thus, we have identified that both systems are a typical cluster glass. We infer that this mechanism is common to SG-freezing occurring in diluted systems with concentrations near below the percolation concentration. (4) Mn_xMg_<1-x>TiO_3 : The x-T magnetic phase diagram was determined on the whole. We have found that the spin system changes at x-0.57 from an AF-system showing the random-field effect to an SG-system. Less
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