DOI: 10.5281/zenodo.15853677
title: Dataset for Emergent ferromagnetism and interface exchange bias in self‑assembled copper‑fullerene hybrid nanostructures

description: Here, thin ­CuxC60 OIH films were fabricated by simultaneous  deposition of pure Cu (99.99 mass. % Cu, Mateck) and pure ­C60 (99.95 mass.% ­C60, MER) on Si(100)  substrates with a size of 5 mm × 10 mm at the substrate temperature of 100 °C in high vacuum of 1­ 0−6 mbar. The deposition was performed from independent sources, namely from an electron gun (Cu deposition) and from an effusion cell (­ C60 deposition), which proper operation controlled by digital controllers (FuG Elektronik) allowed us to adjust deposition rates to reach the required concentration of Cu, x, in the deposited Cu and C ­ 60 mixture (x is a number of Cu atoms per one C ­ 60 molecule).Control of quality of the depositing C ­ uxC60 films during deposition process was carried by quartz thickness monitor  (deposition rate, rd), effusion cell temperature (Tec), electron beam current (Ieg), substrate temperature (Ts), and by vacuum control (Pv). The deposition parameters were kept constant during deposition process and were set as following: Ieg = 16 mA and 18 mA (for LC and HC, respectively); Ts = 100 °C; Pv = 4 × ­10−6 mbar (working vacuum). Time of the deposition process was fixed as 600 s. Change of the depositing samples from LC to HC (as well as the parameter Ieg) was carried out in situ without interruption of the depo- sition process (shutter was closed during the sample change). Between the experiments, the samples were kept in vacuum. The value of x is verified by Rutherford backscattering spectrometry (RBS) analysis of the deposited ­CuxC60 sample. In this study, we fabricated the C ­ uxC60 OIH samples with two Cu concentrations, namely x = 3.6 (low Cu content, LC) and x = 8.5 (high Cu content, HC). The RBS spectra were recorded using a 2 MeV ­He+-ion beam generated by a 6-MeV Tandetron accelerator in a vacuum of ­10−7 mbar. The recorded RBS spectra were analyzed using SIMNRA computer code [47]. The nanostructure of the SA ­CuxC60 hybrid films was verified and studied by transmission electron microscopy(TEM) using a FEI Tecnai TF20 X-twin microscope operated at 200 kV. TEM images and selected-area electron diffraction (SAED) patterns were recorded by means of a Gatan UltraScan CCD camera with a resolution of (2048 × 2048) pixels using DigitalMicrograph. The SAED patterns were evaluated using the ProcessDiffraction software package [48]. Samples for TEM analysis were prepared by scratching the deposited C ­ uxC60 films on holey-carbon-coated Cu grids.Raman spectra of the self-assembled C  ­ uxC60 hybrid films were recorded using the LabRAM HR Evaluation Raman spectrometer from HORIBA Scientific. The spectrom-eter is combined with confocal optical microscopy with a resolution of 1 μm. The excitation of the Raman spectra was carried out by SHG Nd:YAG laser with a wavelengthof 532 nm. The Raman spectra of the self-assembled hybrid films were recorded under ambient conditions at RT at a laser power density of 10 mW/cm2.Magnetic properties of the self-assembled C ­ uxC60 films were studied by a superconductive quantum interference device (SQUID) magnetometer (MPMS7 from QuantumDesign) with a resolution of ­10−8 emu and with the highest magnetic field of 7 T. In the present experiments, the magnetic field, H, was applied with in-plane orientation relative to the ­CuxC60 sample. The magnetization curves M(H) were measured with the cyclic variations of the magnetic field H with an amplitude of 0.2 T. The  magnetization was studied at the different temperatures T in the interval from 100 to 300 K and at 2 K.