The Wrong Way to Write a Paper

Maybe eighteen months or even two years ago I notice that the conference on Hyperfine Interactions and Nuclear Quadrupole Interactions (HFINQI) was coming to Canberra. I always take a close look at conferences that come to Canberra, because I work there.   At the time I was working on a project studying the properties of some magnetically unusual materials, the MPS3 family of compounds.  In particular, we were looking at ones that contained 50:50 ratios of two different magnetic transition metals on the M site, and we had found some interesting behaviour in Fe0.5Ni0.5PS3.  This compound seems to show time-dependent magnetic properties suggesting glassiness and disorder.

Now, iron-containing materials can be studied using Mössbauer spectroscopy, which is sensitive to the crystal and magnetic environments of the Fe atoms, in this case Fe2+ ions.

My students and I had studied the materials using magnetometry and neutron diffraction, but if I wanted to put the work in to HFINQI I needed a hyperfine technique, which Mössbauer is.  I contacted Glen Stewart at PEMS at UNSW Canberra, who is an expert in Mössbauer and we talked over an experiment.  In the end, Glen collected some lovely data and was able to fit it with a really nice model, and here’s a picture:

Mossbauer figure

A sample of the 57Fe-Mössbauer spectra recorded for Fe0.5Ni0.5PS3 as a function of temperature. In each case, the fitted theory (black line) is a sum of three magnetically-split sextets (coloured lines) which are associated with three distinct magnetic Fe-site environments.

We find that the time-dependence is not apparent in the Mössbauer, which is not surprising as it is a slow technique.  We also find that the Fe environments are not random, which is perhaps the most significant result, as it will relate to the interactions between magnetic species and so to the magnetic properties.

Now, while putting a paper into HFINQI prompted the Mössbauer work, which is a backwards way of choosing what science to do, it was by no means a silly experiment to do, as the site-symmetry information available from the technique complements the crystal symmetry information from neutron diffraction, and has indeed enhanced our understanding of the compound.

The paper is available (paywalled, I’m sorry to say) at http://dx.doi.org/10.1007/s10751-014-1108-6.

Chemical and magnetic ordering in Fe0.5Ni0.5PS3 by D.J.Goossens · G.A.Stewart · W.T.Lee · A.J.Studer, Hyperfine Interactions (full reference not yet available as of Dec 27, 2014).

 

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About Darren

I'm a scientist by training, based in Australia.

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