AMPHIBIAN CSIC experimental data insitu exsitu PXRD NPD

During the past decade, CoFe2O4 (hard)/Co–Fe alloy (soft) magnetic nanocomposites have been routinely prepared by partial reduction of CoFe2O4 nanoparticles. Monoxide (i.e., FeO or CoO) has often been detected as a byproduct of the reduction, although it remains unclear whether the formation of this phase occurs during the reduction itself or at a later stage. Here, a novel reaction cell was designed to monitor the reduction in situ using synchrotron powder X-ray diffraction (PXRD). Sequential Rietveld refinements of the in situ data yielded time-resolved information on the sample composition and confirmed that the monoxide is generated as an intermediate phase. The macroscopic magnetic properties of samples at different reduction stages were measured by means of vibrating sample magnetometry (VSM), revealing a magnetic softening with increasing soft phase content, which was too pronounced to be exclusively explained by the introduction of soft material in the system. The elemental compositions of the constituent phases were obtained from joint Rietveld refinements of ex situ high-resolution PXRD and neutron powder diffraction (NPD) data. It was found that the alloy has a tendency to emerge in a Co-rich form, inducing a Co deficiency on the remaining spinel phase, which can explain the early softening of the magnetic material.

The different datasets are divided in folders as follows: 1. In situ experiments. The article is based on 7 different in situ experiments: a. 400C_5mLmin_fr10; b. 400C_10mLmin_fr23; c. 400C_20mLmin_fr6; d. 400C_30mLmin_fr12; e. 300C_10mLmin_fr4; f. 350C_10mLmin_fr18; g. 500C_10mLmin_fr9. (Due to space limitations, only the data corresponding to the experiment c were uploaded to this repository. The remaining data are accessible through private communication with Cecilia Granados-Miralles, c.granados.miralles@icv.csic.es). The folder “c_400C_20mLmin_fr6” contains in situ PXRD data (time resolution=5 s) collected during reduction at the temperature and gas flow indicated in the folder name (i.e. 400C_20mLmin stands for 400 °C and 20 mL/min). The temperature indicated in the file names is the set temperature but the sample temperature is the indicated in the folder name (i.e. Tset430 led to a sample temperature of 400 °C). Heating started on the frame indicated in the folder name (i.e. fr6 stands for frame 6). This folder contains 2D-diffraction images in *.tif format, which may be opened with the Python-based program for on-the-fly data processing and exploration of two-dimensional X-ray diffraction area detector data, available for free download at http://www.clemensprescher.com/programs/dioptas.