Neutron Scattering Studies of Low Dimensional Magnets: DMACuCl3 and LiMPO4 (M=Co,Mn)

Wei Tian (Ames Lab)

Low dimensional magnets exhibit a variety of novel magnetic behavior and remain one of the most active research areas. Neutron scattering has been broadly recognized as a powerful tool providing unique information about the nature of the quantum ground state and excitations. In this talk I present results of inelastic neutron scattering (INS) studies of two magnetic systems: DMACuCl3 and LiMPO4 (M=Co, Mn). DMACuCl3 had been proposed as a model spin ½ ferromagnetic-antiferromagnetic alternating chains. It was claimed later that the field dependent magnetization was more consistent with a model of weakly coupled ferromagnetic and antiferromagnetic dimers. Our INS results show that the magnetic spectrum of DMACuCl3 is consistent with an alternating-sign chain. However, the direction of the chain is perpendicular to the previous proposed chain direction, and there are actually two distinct chains in the system. LiMPO4 are antiferromagnetic insulators exhibiting large magnetoelectric effects in the antiferromagnetic phase. INS studies of the spin dynamics of LiMnPO4 and LiCoPO4 indicate that LiMnPO4 is magnetic quasi-2D while the single ion anisotropy in LiCoPO4 is comparable to the nearest-neighbor magnetic exchange interaction rendering Ising-type behavior of LiCoPO4.

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