| Co-Investigator(Kenkyū-buntansha) |
MORIMOTO Setsu Ochanomizu University, Faculty of Science, Asistant, 理学部, 助手 (90017195)
MORIMOTO Setsu Ochanomizu University, Faculty of Science, Asistant (90017195)
MORIMOTO Setsu Ochanomizu University, Faculty of Science, Asistant (90017195)
MORIMOTO Setsu Ochanomizu University, Faculty of Science, Asistant (90017195)
MORIMOTO Setsu Ochanomizu University, Faculty of Science, Asistant (90017195)
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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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