Magnetism and Structure of Magnetic Multilayers Based on the Fully Spin Polarized Heusler Alloys Co2MnGe and Co2MnSn

Abstract

Book Series\tLecture Notes in Physics Publisher\tSpringer Berlin / Heidelberg ISSN\t1616-6361 Volume\tVolume 676/2005 Book\tHalf-metallic Alloys DOI\t10.1007/b137760 Copyright\t2005 ISBN\t978-3-540-27719-4 DOI\t10.1007/11506256_3 Pages\t67-112 Subject Collection\tPhysics and Astronomy SpringerLink Date\tFriday, September 23, 2005 Our Introduction starts with a short general review of the magnetic and structural properties of the Heusler compounds which are under discussion in this book. Then, more specifically, we come to the discussion of our experimental results on multilayers composed of the Heusler alloys Co2MnGe and Co2MnSn with V or Au as interlayers. The experimental methods we apply combine magnetization and magnetoresistivity measurements, x–ray diffraction and reflectivity, soft x-ray magnetic circular dichroism and spin polarized neutron reflectivity. We find that below a critical thickness of the Heusler layers at typically dcr = 1.5 nm the ferromagnetic order is lost and spin glass order occurs instead. For very thin ferromagnetic Heusler layers there are pecularities in the magnetic order which are unusual when compared to conventional ferromagnetic transition metal multilayer systems. In [Co2MnGe/Au] multilayers there is an exchange bias shift at the ferromagnetic hysteresis loops at low temperatures caused by spin glass ordering at the interface. In [Co2MnGe/V] multilayers we observe an antiferromagnetic interlayer long range ordering below a well defined Nel temperature originating from the dipolar stray fields at the magnetically rough Heusler layer interfaces.