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oe1(光电查) - 科学论文

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?? 中文（中国） ▾

  • The Magnetic Properties of 1111-type Diluted Magnetic Semiconductor (La1?xBax)(Zn1?xMnx)AsO in the Low Doping Regime

    摘要： We investigated the magnetic properties of (La1?xBax)(Zn1?xMnx)AsO with x varying from 0.005 to 0.05 at an external magnetic field of 1000 Oe. For doping levels of x ≤ 0.01, the system remains paramagnetic down to the lowest measurable temperature of 2 K. Only when the doping level increases to x = 0.02 does the ferromagnetic ordering appear. Our analysis indicates that antiferromagnetic exchange interactions dominate for x ≤ 0.01, as shown by the negative Weiss temperature fitted from the magnetization data. The Weiss temperature becomes positive, i.e., ferromagnetic coupling starts to dominate, for x ≥ 0.02. The Mn-Mn spin interaction parameter |2J/kB| is estimated to be in the order of 10 K for both x ≤ 0.01 (antiferromagnetic ordered state) and x ≥ 0.02 (ferromagnetic ordered state). Our results unequivocally demonstrate the competition between ferromagnetic and antiferromagnetic exchange interactions in carrier-mediated ferromagnetic systems.

    关键词： ferromagnetic ordering,ferromagnetic coupling,antiferromagnetic exchange interaction,carrier-mediated

    更新于2025-09-23 15:22:29

  • Heterodimer on MgO

    摘要： We report on the magnetic properties of HoCo dimers as a model system for the smallest intermetallic compound of a lanthanide and a transition metal atom. The dimers are adsorbed on ultrathin MgO(100) films grown on Ag(100). New for 4f elements, we detect inelastic excitations with scanning tunneling spectroscopy and prove their magnetic origin by applying an external magnetic field. In combination with density functional theory and spin Hamiltonian analysis, we determine the magnetic level distribution, as well as sign and magnitude of the exchange interaction between the two atoms. In contrast to typical 4f ? 3d bulk compounds, we find ferromagnetic coupling in the dimer.

    关键词： ferromagnetic coupling,heterodimer,density functional theory,spin excitations,scanning tunneling spectroscopy

    更新于2025-09-04 15:30:14