# Magnetic properties of a helical spin chain with alternating isotropic and anisotropic spins: Magnetization plateaus and finite entropy

Chandra, Ravi V and Ramasesha, S and Sen, Diptiman (2004) Magnetic properties of a helical spin chain with alternating isotropic and anisotropic spins: Magnetization plateaus and finite entropy. In: Physical Review B: Condensed Matter and Materials Physics, 70 (14). 144404/1-144404/8.

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## Abstract

We propose a model which could explain some of the unusual magnetic properties observed for the onedimensional helical spin system $Co(hfac)_2NITPhOMe.$ One of these properties is that the magnetization shows some plateaus if a magnetic field is applied along the helical axis. The system consists of cobalt ions (which have easy axes which are tilted at an angle $\theta_i$ with respect to the helical axis) and organic radicals alternating with each other. We consider a model in which the tilt angles $\theta_i$ are allowed to vary with i with period three. Using the transfer matrix approach, we show that for certain patterns of $\theta_i$, the model exhibits the magnetization plateaus mentioned above. At the ends of the plateaus, we find that the entropy is finite even at very low temperatures, while the magnetic susceptibility and specific heat also show some interesting features.

Item Type: Journal Article The copyright of this article belongs to American Physical Society. Division of Chemical Sciences > Solid State & Structural Chemistry UnitDivision of Physical & Mathematical Sciences > Centre for High Energy Physics 12 Apr 2006 19 Sep 2010 04:25 http://eprints.iisc.ernet.in/id/eprint/6117