GIANT SPIN FLUCTUATIONS IN LAVES PHASE YMn_2

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By substituting Sc for Y, an itinerant antiferromagnt YMn_2 becomes a Pauli paramagnet. We have shown by thermal expansion analysis and neutron scattering, experiments that giant spin fluctuations are thermally excited. In this research, we have measured the low temperature specific heart, electric resistivity and have shown that this system has characteristics of heavy Fermion systems although it contains neither 4f nor 5f element. In addition, we have investigated the magnetism and other properties of Y(Sc)(Mn_<1-x>Al_x)_2 system and have shown that anomalous properties of the present system may originate in frustrative magnetic interactions. Main results for each year are given below:1987(1) The low temperature specific heat of Y_<0.95>Sc_<0.05>Mn_2 was measured. It has been revealed that the electronic specific heat coefficient of this material is the largest in 3d metallic systems as gamma=145mJ/mol・K^2. (2) The temperature dependence of electrical resistivity was measured for Y_<0.95>Sc_<0.05>Mn_2 from 4.2K to 300K. We have shown that the coefficient of T^2 term is very large as A=0.25mu OMEGA cm/K^2,which is comparable to that of heavy Fermion systems.1988(1) The system for low temperature specific heat measurements was automated by using a micro-computer. Using this system, the low temperature specific heats of Y_<1-x>Sc_xMn_2 were measured and the gamma value was obtained as a function of concentration. The system for low temperature specific heat measurements was automated by using (2) The electric resistivity of Y_<0.95>Sc_<0.05>(Mn_<1-x>Al_x)_2 was measured as a function of temperature and revealed that the system transfers from a heavy Fermion like to a local moment system.1989Magnetic susceptibility and low temperature specific heat of Y_<0.95>Sc_<0.05>(Mn_<1-x>Al_x)_2 system were measured. We explained the characteristic properties of these systems as a result of magnetic frustrations.