Magnetic order beyond RKKY in the classical Kondo latticeKalpataru Pradhan and Pinaki Majumdar
Harish-Chandra Research Institute - Chhatnag Road, Jhusi, Allahabad 211019, India
received 16 November 2008; accepted in final form 20 January 2009; published February 2009
published online 13 February 2009
We study the Kondo lattice model of band electrons coupled to classical spins, in three dimensions, using a combination of variational calculation and Monte Carlo. We use the weak-coupling “RKKY” window and the strong-coupling regime as benchmarks, but focus on the physically relevant intermediate-coupling regime. Even for modest electron-spin coupling the phase boundaries move away from the RKKY results, the non-interacting Fermi surface no longer dictates magnetic order, and weak-coupling “spiral” phases give way to collinear order. We use these results to revisit the classic problem of 4f magnetism and demonstrate how both electronic structure and coupling effects beyond RKKY control the magnetism in these materials.
75.30.Kz - Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.).
75.30.Et - Exchange and superexchange interactions.
71.20.Eh - Rare earth metals and alloys.
© EPLA 2009