Noncollinear magnetic order in antiferromagnetic and weak-ferromagnetic transition-metal clusters Article uri icon

abstract

  • The magnetic properties of transition-metal clusters having N≤19 atoms are determined using a d-band model Hamiltonian within the unrestricted Hartree-Fock approximation, which allows noncollinear magnetic arrangements of the local magnetic moments μl at different cluster atoms l. Results are given for μl and for the average magnetic moment per atom μN = (1/N)|Σl μl| as a function of d-band filling, nd, and J/W (J refers to the d-electron effective exchange integral and W to the d-band width). It is shown that compact clusters near half-band filling present antiferromagnetic-like noncollinear magnetic arrangements, which attempt to minimize antiferromagnetic frustration in nonbipartite structures. The resulting μn are very small, in agreement with experiments in CrN clusters (typically μN≤0.5 μB for N≤19). For nd≈6.5-7 as a function of J/W, the clusters undergo a transition from antiferromagnetic- to ferromagnetic-like orders. Thereby a novel physical picture for the onset of ferromagnetism is discussed. Comparison is made with the available noncollinear ab initio results.

publication date

  • 2000-01-01