Numerical Renormalization Group calculations of the magnetization of isotropic and anisotropic Kondo impurities
Dec, 2012Citations per year
Abstract: (arXiv)
We study a Kondo impurity model with additional uniaxial anisotropy D in a non-zero magnetic field B using the Numerical Renormalization Group (NRG). The ratio g_e/g_S of electron and impurity g-factor is regarded as a free parameter and, in particular, the special cases of a 'local' (g_e=0) and 'bulk' (g_e=g_S) field are considered. For a bulk field, the relationship between the impurity magnetization M and the impurity contribution to the magnetization M_imp is investigated. Furthermore, we study how the value of g_e affects the impurity magnetization curves. In case of an isotropic impurity with g_e=g_S, it is demonstrated that at zero temperature M(B), unlike M_imp(B), does not display universal behavior. With additional 'easy axis' anisotropy, the impurity magnetization is well described by a shifted and rescaled Brillouin function on energy scales that are small compared to |D|. In case of 'hard axis' anisotropy, the magnetization curves can feature steps which are due to field-induced pseudo-spin-1/2 Kondo effects. For large anisotropy and a local field, these screening effects are described by an anisotropic spin-1/2 Kondo model with an additional scattering term that is spin-dependent (in contrast to ordinary potential scattering). Our study is motivated by the question how the magnetic properties of a deposited magnetic molecule are modified by the interaction with a non-magnetic metallic surface.Note:
- 26 pages, 18 figures
- 75.30.Cr
- 75.60.Ej
- 73.20.Hb
- 75.50.Xx
- 75.30.Gw
- temperature: 0
- spin: dependence
- magnetization
- anisotropy
- renormalization group
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