Spin–Spin Correlation Length in MnSi Thin Films

Abstract

Thin MnSi films have been prepared on Si(111) by molecular beam epitaxy under simultaneous evaporation of Mn and Si. RHEED analysis in combination with TEM investigation reveals that this codeposition technique leads to smooth films. Resistivity measurements show a metallic behavior that is qualitatively the same as for bulk MnSi. The magnetic ordering temperature T ord of 43 K, which has been determined from resistivity data and by SQUID magnetometry, is considerably enhanced compared to the bulk value. For the thinnest films, however, a decrease of T ord is observed which is explained by the reduction of the spin–spin interaction near the surfaces of the film. Recently, it has been stated, that the spin–spin correlation length is much larger than known from other itinerant magnetic materials. In contrast, we show that the coupling range can be estimated as 7 monolayers and does not exceed the values of common magnets.