Superconducting quantum interference device magnetometry during ultrahigh vacuum growth

Abstract

An in situ study of the absolute magnetic moment of thin ferromagnetic films grown in ultrahigh vacuum (UHV) is described. The moments are measured using a newly innovated technique, rotating sample superconducting quantum interference device (SQUID) magnetometry (RSSM), in which the sample is spun at low frequency close to an ex situ second derivative superconducting pickup loop structure coupled to a rf SQUID. The sensitivity of the measurements is ≊10-6 emu, which corresponds to 1/10 of an atomic layer of Fe over a 0.5 cm2 area, and the geometry of the pickup loops makes the magnetometer very insensitive to background laboratory noise. The moment of Cr grown on Fe was measured. It was determined that the first two layers of Cr have an average moment of 0.75 μB per atom, and are antiferromagnetically aligned to the Fe film moment. The simplicity of RSSM and the fact that the absolute moment is measured makes this a powerful new approach for characterization of magnetic samples in UHV. © 1994 American Institute of Physics.