Study of the Ground State Properties in Random Magnetic Systems

It is the aim of the present project to clarify the ground state properties of the random magneticsystems with competing spin anisotropies and with competing exchange interactions.For the study ofcompeting spin anisotropies system, we have chosen the materials，< fec_ (1-x)> < co_x > < cl_2 > < h_2o > (FCC2)，< fe _(1 - x)> < co _ x > < 2欧冠> (fcc) and < fe _(1 - x)> < co _ x > 2 < br > (fcb). it is found from the neutronscattering study on FCC2 that the spin components are totally decoupled. FCC2是第一次试验of an ideal antiferromagnet with competing spin anisotropies. We have found <Fe^(2+)> localizedmagnetic excitations in the Co-rich antiferromagnetic phase of FCC2 from the ESR experiments at veryhigh frequency and field. From the analysis of the ESR experimentsit is shown that the <Fe^(2+)> spins make a large angle with the <Co^(2+)> spins even in the Co-richphase.我们有性能模拟研究on FCC and FCB.这些研究成果give us importantinformations on the spin orderings and the ground state properties of the random magnets withcompeting 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 > andantiferromagnet < rb_2 > < mncl_4 > . The single crystals of < rb_2 > < mn_ (1-x)> < cr_x > < cl_4 > grown for这个研究已经被characterized by means of susceptibility and ESR measurements.这是发现的the random magnet is a quasi-2d XY spin-glass(SG). No material has beenreported that exhibits a 2d XY SG behaviorand < rb_2 > < mn_ (1-x)> < cr_x > < cl_4 > is the first example of a 2d XY SG. In the Cr-rich concentrationregion,我们发现了一个re-entrant spin-glass(RSG) transition. The NMR and neutron scattering experiments showthe zero field cooled RSG state consists of ferromagnetic domains and vortices. These resultsgive us an important information on the ground state properties of the 2d XY SG。

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.