Ab initio calculations are presented for magnetic properties of small islands of 3d, 4d, and 5d adatoms on the Ag͑001͒ surface, intermixed with Ag substrate atoms. We show that the intermixing of small 4d and 5d clusters can lead to an unexpected enhancement of the local moments and is very different from the intermixing behavior found in the monolayer regime. ͓S0163-1829͑98͒05148-0͔Unusual magnetic properties of nonmagnetic in bulk 4d and 5d elements have been predicted for monolayers, 1 free, 2 and supported clusters 3 in ab initio calculations within the local spin-density approximation ͑LSDA͒ of the densityfunctional theory. Naturally, these unexpected results attracted several experimental groups to test the possibility of the magnetism in new systems. [4][5][6][7] Due to theoretical conclusions, the main possible candidates for new magnetic properties might be Ru and Rh among the 4d systems, and Os and Ir among the 5d systems. For monolayers and supported clusters, the surfaces of Ag and Au are interesting substrates due to the weak hybridization with the transition-metal atoms. Evidence of 4d magnetism has been found in experiments of Cox et al. 5 for free Rh and Ru clusters. Experiments of Pfandzelter et al. 6 have shown that Ru monolayers are magnetic on C͑0001͒ surface. The confirmation of the magnetism of Nb adatoms and small Ru and Rh clusters on the Ag surface, which has been predicted in our group, 3 has been recently reported.7 At the same time, the magnetism of 4d and 5d monolayers on noble metals has not been found in experiments. 4 This seems to be connected with structural imperfections ͑islanding, surface roughness, interdiffusion͒ which exist in real experiments with noble metal surfaces. 8 For example, recent scanning tunneling microscopy techniques revealed that for Rh on Ag͑001͒ the direct exchange with Ag surface atoms and the growth of mixed Rh/Ag adislands are very important processes at the initial stage of epitaxial growth.9 Ab initio calculations of two-dimensional random alloys RhAg and RuAg on a Ag͑001͒ performed by Turek et al. 10 demonstrated that magnetic moments of Rh and Ru are strongly reduced and in some cases magnetism of Rh and Ru monolayers is totally suppressed due to the intermixing with the substrate. These results can be used to explain the null results in magnetic experiments with Rh and Ru monolayers on noble metal substrates. They also show that in the one-or two-monolayer regime the mixing of Rh and Ru with Ag atoms always leads to a reduction of magnetic moments.The main goal of our paper is to show that at the initial stage of monolayer growth, when small mixed adislands are formed, the intermixing of small 4d and 5d islands with Ag substrate atoms has a very different effect and is determined by a cluster size effect, which can lead to an unexpected enhancement of magnetic moments in mixed adislands.Our calculations are based on density-functional theory in the LSDA and the Korringa-Kohn-Rostoker Green'sfunction method for impurities and clusters on metal su...
Starting from a pseudopotential calculation for h.c.p. beryllium the (Jompton profiles are cal- (100) und (1 10) werden durch weitgehende Einbeziehung der O r t h o g o n a l i t l i t k t u r e n verbessert.Es wird eine bemerkenswert grol3e Anisotropie fur I(o01) -I(l02) bzw. I(00l) -1 < 1 1 2 ) gefunden.Der Beitrag des Korrelationsschwanzes in der Impulsverteilung wird abgeschitzt. Beim Vergleich mit Messungen hoher Auflosung mu0 die Korrelation beriicksichtigt werden.
Elektronenzustandsdichte in d e r Lavesphase MgZn2 Von G. LEHMANN, P. RENNERT, M. TAUT und H. WONN In einer kUrzlich erschienenen Arbeit (I) wird geschildert, wie mit d e r Pseudo-
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