Tuning the orbital moment in transition metal compounds using ligand states

Abstract

The influence of ligand states on the orbital magnetism of a 3d atom in a ferromagnetic compound has been studied using an ab initio technique. It is shown, using VAu4, MnAu4 and VPt3 as examples, that the large spin-orbit coupling of the 5d atom is responsible for the reversal of the coupling between the V(Mn) spin and orbital moments with respect to that for similar compounds. The VAu4 compound has a large magneto-crystalline anisotropy (MCA) and the spin-up states are completely occupied, which makes its MCA proportional to the orbital moment anisotropy as stated by Bruno's perturbative formula (Bruno P 1989 Phys. Rev. B 39 865). For the latter compound it is also shown that a partial substitution of copper for gold decreases the vanadium orbital moment and hence the MCA. The ligand state effects on the orbital moment together with this alloying procedure may initiate a new approach in the search for ultra-soft magnetic materials.

Ab-initio calculation of effective exchange interactions, spin waves, and Curie temperature in L21- and L12-type local moment ferromagnets

“…As we move from V to Cr and then to Mn the extra electrons occupy majority-spin states and the minority-spin states are above the Fermi level. This is also reflected on the X-resolved spin magnetic moments in Table 1 [45]. Regarding the exchange parameters in Fig.…”

“…Thus as we move from V to Mn the calculated spin magnetic moments come closer to the experimental values and so do the Curie temperatures. The large discrepancy exhibited for V is a well-known problem of densityfunctional-theory-based calculations and can be traced also to other V-based compounds [45]. Regarding the exchange parameters in Fig.…”

“…The Mn-based compounds have attracted a lot of interest due to the localized nature of Mn spin moments [37]. The XPt 3 compounds on the other hand have also attracted considerable attention both theoretically [38,39,40,41,42,43,44,45] and experimentally [46,47,48,49,50,51,52,53] due to the variety of magnetic order which they exhibit and due to the large magnetocrystalline anisotropy shown by CrPt 3 [44] and CoPt 3 [50] which makes the latter alloys attractive for magnetic storage devices. Moreover these systems are prototypes for studying the induced magnetism at the Pt site due to the strong hybridization between the d-orbitals of the transition-metal atoms and the platinum atoms [40].…”

Systematic theoretical study of the spin and orbital magnetic moments of4dand5dinterfaces with Fe films

“…1 where the atomic values of these quantities are shown. Although strictly valid only for single atoms, this rule seems to be applicable also to solids with only a few exceptions, such as U metal [22] and vanadium in VAu 4 [23] and VPt 3 [24]. The violation reported in Fe/W multilayers [21] seems surprising, since W as an impurity and in alloys does not show this violation [11,25].…”

Aplicación de nuevas sondas microscópicas al estudio del magnetismo de las fases de laver RCO2

“…De hecho son muy escasos los sistemas en los que se ha encontrado que el momento orbital y de espín no están alineados como predice la tercera regla de Hund. En concreto, se ha predicho teóricamente una pseudo-violación de la tercera regla de Hund para momentos inducidos en uranio [105] y en VAu 2 ordenado magnéticamente [69,68]. La primera observación experimental de este fenómeno fue llevada a cabo por Wilhelm y colaboradores en 2001 mediante medidas de XMCD en estructuras de multicapas de Fe/W [193].…”