### Session Z36: Focus Session: Bulk Properties of Complex Oxides -- 4d and 5d Systems

11:15 AM–2:15 PM, Friday, March 19, 2010
Room: E146

Chair: Rongying Jin, Louisiana State University

Abstract ID: BAPS.2010.MAR.Z36.5

### Abstract: Z36.00005 : Unusual interlayer magnetic coupling in quasi 2-D heavy-mass nearly ferromagnetic state of (Sr$_{1-x}$Ca$_{x})_{3}$Ru$_{2}$O$_{7}$

12:03 PM–12:15 PM

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#### Authors:

D. Fobes
(Department of Physics, Tulane University, New Orleans, LA 70118)

J. Peng
(Department of Physics, Tulane University, New Orleans, LA 70118)

Z. Qu
(Department of Physics, Tulane University, New Orleans, LA 70118)

T. J. Liu
(Department of Physics, Tulane University, New Orleans, LA 70118)

Z. Q. Mao
(Department of Physics, Tulane University, New Orleans, LA 70118)

A. Rotaru
(Department of Physics, University of New Orleans, New Orleans, LA 70148)

L. Spinu
(Department of Physics, University of New Orleans, New Orleans, LA 70148)

Perovskite ruthenates exhibit a wide range of complex magnetic ground states. In this talk we focus on an unusual heavy-mass, nearly ferromagnetic state with an extremely large Wilson ratio (Z. Qu \textit{et al.}, Phys. Rev. B \textbf{78} R180407 (2008)). Despite considerable FM correlations, this state never develops long-range FM order, instead freezing into a cluster-spin-glass (CSG) state. We have further investigated this magnetic state through in-plane angular dependence of magnetoresistivity and magnetization on (Sr$_{0.62}$Ca$_{0.38})_{3}$Ru$_{2}$O$_{7}$. The in-plane magnetoresistivity $\rho_{ab}(\phi)$ at high magnetic fields reveals a change in anisotropy symmetry from 2-fold to 4-fold at the frozen temperature $T_{f}$ of the CSG phase, whereas inter-planar magnetoresistivity $\rho_{c}(\phi)$ at high fields only exhibits 4-fold symmetry. For low magnetic fields, both $\rho_{ab}$ and $\rho_{c}$ only exhibit anisotropy below $T_{f}$, also with 4-fold symmetry. Angle-dependent magnetization data reveal that at high field the anisotropy exhibits 8-fold symmetry for $T > T_{f}$. However, for $T < T_{f}$, an additional asymmetric 2-fold anisotropy develops. These results may indicate non-traditional interlayer magnetic coupling, one possible scenario involving perpendicular spin stacking between alternate layers.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.MAR.Z36.5