First (quasi) in-situ neutron reflectivity measurements on ultrathin magnetic films at MARIA

The magnetic neutron reflectometer with high incident angle (MARIA) at the Heinz Maier- Leibnitz Zentrum (MLZ) in Garching, Germany is a dedicated instrument for polarized neutron reflectometry of thin films [1]. However, due to limited space a UHV system for thin film growth and in-situ measurements cannot be placed on-site.Recently, we have solved this problem by developing a handy mini UHV chamber which is capable for both, sample transfer and quasi in-situ measurements at the neutron reflectivity instrument, respectively. Quasi in-situ polarized neutron reflectivity (PNR) measurements can be performed at room temperature in magnetic fields of up to 600 mT. Our solution consists of a DN CF-40 cube with two opposing sapphire windows for the neutron beam, a combined non evaporable getter and ion pump for keeping the vacuum, a wobble stick, which is needed for in-situ sample transfer and also serves as sample holder for samples of up to 1 cm2 and a valve for sample exchange by mounting the chamber on the MBE system. The pressure in the transfer chamber is kept in the 10−10 mbar range during transport and PNR measurement.We present the first polarized neutron reflectivity measurements on a 2 nm Co thin film which was grown in our MBE setup and measured afterwards at MARIA at room temperature in a magnetic field of 300 mT in the Q-range up to 0.2 Å-1. The data evaluation clearly shows no oxidation of the Co film. So, samples which are delicate to handle in ambient conditions can be successfully measured using our handy UHV chamber.Booking of the access to the MBE system as well as the transport chamber for measuring is possible via the MLZ user office system and the nanoscience foundry and fine analysis project (NFFA, www.nffa.eu) in combination with an application for a beam time at the neutron instrument MARIA.This project is part has received funding from the EU’s H2020 research and innovation programme under grant agreement n. 654360.[1] S. Mattauch, A. Koutsioubas, and S. Pütter, Journal of large-scale research facilities 1, A8 (2015), (www.mlz-garching.de)