Spin Dynamics and Onset of Magnetism in LiY1-xHoxF4

Michael J. Graf (Boston College) DMR 0710525

Increasing the amount of holmium doped into LiYF4 (below) takes it from single-ion quantum magnet to bulk ferromagnet. Muon spin rotation (SR), which exploits muons produced at a particle accelerator in order to probe magnetism in solids (right), is an effective probe of this magnetism and its evolution with Ho concentration.

For example, we found that the rotation of a muon in a magnetic field is dramatically altered at theoretically-predicted magnetic field values where the energy states of the Ho ion are strongly coupled together [1].

We are now studying how the dynamics are modified when we ‘build’ a bulk ferromagnet by increasing the Ho concentration x.

[1] Graf et al. Phys. Rev. Lett. 99, 267203 (2007).

www.isis.ral.ac.uk

A high priority has been training undergraduate and graduate students, with emphasis on muon spin relaxation (SR) studies at international facilities.

Jeff Klatsky ‘08 (now in the Physics Ph.D. program at Florida State) analyzed SR data for his senior thesis, and attended a 5-day SR workshop held at the ISIS facilty in the UK (upper foto). Graduate student Ryan Johnson (inset) conducted SR experiments (May 2008) at the Paul Scherrer Institute, Switzerland. Both co-authored papers presented at the 25th International Conference on Low Temperature Physics (Aug. 2008)

This summer Karen Chen ’10 joined the program, shown on the left in the lower foto, along with Boston College summer REU (DMR-0649169) participant Caleigh Samuels ‘10 of Radford University.

Spin Dynamics and Onset of Magnetism in LiY1-xHoxF4

Michael J. Graf (Boston College) DMR 0710525