Non-collinear structure of Cr trimer on the surface of non-magnetic metals

Magnetic structure of Cr trimer clusters on non-magnetic metal substrate ha s been calculated by recursion method within Anderson model. The values of the moments are enhanced relatively to bulk bcc Cr due to the reduction of coordination number. Angles between the moments depend on the relations bet ween hopping parameters V-ij, determined by the interatomic distance in the cluster. We performed systematic calculations of the ground state for diff erent values of parameters V-12 = V-13 and V-23. For V-12 << V-23 ground st ate corresponds to moments on the atoms 2 and 3 with opposite direction, wh ereas the moment on atom 1 is perpendicular to them. For V-12 = V-23 the an gle between each pair of moments equals 2 pi/3 and the total moment of the trimer is zero. A decrease of V-23 versus V-12 leads to collinear state wit h moment on the atom 1 antiparallel to the moments on second and third. Cal culation in external magnetic field reveals the co-existence of two self-co nsistent states with essentially different total magnetic moments. In weak field these solutions are very close in energy whereas with the increase of the field the state with larger moment is stabilized. (C) 2000 Elsevier Sc ience B.V. All rights reserved.