Antiferromagnetic dipolar ordering in [Co2MnGe/V]N multilayers -: art. no. 214403

We have studied [Co2MnGe/V](N) multilayers with a thickness of the V layers t(V) between 1.5 and 10 nm and a fixed thickness of the Heusler layer t(Co2)MnGe=3 nm by x-ray scattering, neutron reflectivity, and magnetization measurements. In the thickness range t(V)<= 3 nm neutron reflectivity results provide clear evidence for an antiferromagnetic (af) interlayer long-range order below a Neel temperature T-N. The interlayer long range order does not show an oscillating character and is stabilized by a weak af coupling field H-af approximate to 100 Oe. We attribute the af coupling to magnetic dipolar stray fields originating from magnetically rough surfaces of a granular Co2MnGe microstructure. In the thickness range t(V)>= 4 nm the multilayers undergo a cluster glass transition at T-f approximate to 150 K. At high temperatures above T-N or T-f the mutilayers are superparamagnetic with a huge cluster magnetic moment mu(c)>= 10(5)mu(B).