1986 Fiscal Year Final Research Report Summary
Study of the Ground State Properties in Random Magnetic Systems
| Project/Area Number |
60460023
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | The Institute of Physical and Chemical Research(RIKEN) (1986)
Hokkaido University (1985) |
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Principal Investigator |
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| Project Period (FY) |
1985 – 1986
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| Keywords | Random Magnetic System / Ground State / Spin-glass / Competing Spin Anisotropies / OAF Phase / リエントラントスピングラス |
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| Research Abstract |
It is the aim of the present project to clarify the ground state properties of the random magnetic systems with competing spin anisotropies and with competing exchange interactions.
For the study of the competing spin anisotropies system, we have chosen the materials, <Fe_(1-x)> <Co_x> <Cl_2> ・2 <H_2O> (FCC2) , <Fe_(1-x)> <Co_x> <Cl_2> (FCC) and <Fe_(1-x)> <Co_x> <Br_2> (FCB). It is found from the neutron scattering study on FCC2 that the spin components are totally decoupled. FCC2 is the first example of an ideal antiferromagnet with competing spin anisotropies. We have found <Fe^(2+)> localized magnetic excitations in the Co-rich antiferromagnetic phase of FCC2 from the ESR experiments at very high frequency and field. From the analysis of the ESR experiments, it is shown that the <Fe^(2+)> spins make a large angle with the <Co^(2+)> spins even in the Co-rich phase. We have performed similar studies on FCC and FCB. These results give us important informations on the spin orderings and the ground state properties of the random magnets with competing spin anisotropies.
For the study of the competing exchange interactions system, we have chosen the random mixture of a quasi-two-dimensional(2d) ferromagnet <Rb_2> <CrCl_4> and antiferromagnet <Rb_2> <MnCl_4> . The single crystals of <Rb_2> <Mn_(1-x)> <Cr_x> <Cl_4> grown for this study have been characterized by means of susceptibility and ESR measurements. It is found that the random magnet is a typical example of a quasi-2d XY spin-glass(SG). No material has been reported that exhibits a 2d XY SG behavior, and <Rb_2> <Mn_(1-x)> <Cr_x> <Cl_4> is the first example of a 2d XY SG. In the Cr-rich concentration region, we found a re-entrant spin-glass(RSG) transition. The NMR and neutron scattering experiments show that the zero field cooled RSG state consists of ferromagnetic domains and vortices. These results give us an important information on the ground state properties of the 2d XY SG.
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