Underscreened Kondo effect in S=1 magnetic quantum dots: Exchange, anisotropy and temperature effects

Abstract

We present a theoretical analysis of the effects of uniaxial magnetic anisotropy and contact-induced exchange field on the underscreened Kondo effect in S=1 magnetic quantum dots coupled to ferromagnetic leads. First, by using the second-order perturbation theory we show that the coupling to spin-polarized electrode results in an effective exchange field $B_{\mathrm{eff}}$ and an effective magnetic anisotropy $D_{\mathrm{eff}}$. Second, we confirm these findings by using the numerical renormalization group method, which is employed to study the dependence of the quantum dot spectral functions, as well as quantum dot spin, on various parameters of the system. We show that the underscreened Kondo effect is generally suppressed due to the presence of effective exchange field and can be restored by tuning the anisotropy constant, when $|D_{\mathrm{eff}}|=|B_{\mathrm{eff}}|$. The Kondo effect can also be restored by sweeping an external magnetic field, and the restoration occurs twice in a single sweep. From the distance between the restored Kondo resonances one can extract the information about both the exchange field and the effective anisotropy. Finally, we calculate the temperature dependence of linear conductance for the parameters where the Kondo effect is restored and show that the restored Kondo resonances display a universal scaling of $S=1/2$ Kondo effect.

13 pages, 9 figures (version as accepted for publication in Physical Review B)

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Cited by in corpus (12)

• Spin Excitations and Correlations in Scanning Tunneling Spectroscopy
• Spintronic magnetic anisotropy
• Quantum Engineering of Spin and Anisotropy in Magnetic Molecular Junctions
• Generalization of the Time-Dependent Numerical Renormalization Group Method to Finite Temperatures and General Pulses
• Transport mirages in single-molecule devices
• Relaxation dynamics in double-spin systems
• Spin-resolved dynamical conductance of correlated large-spin magnetic molecules
• Transverse anisotropy effects on spin-resolved transport through large-spin molecules
• Dynamical spin accumulation in large-spin magnetic molecules
• Transport of spin-anisotropy without spin currents
• Time-dependent spintronic anisotropy in magnetic molecules
• Giant superconducting proximity effect on spintronic anisotropy