X-ray scattering study of the magnetic phase transitions in GdFe3(BO3)4

The rare earth iron borates have interesting magnetic properties due to the subtle interactions between the rare earth and the iron moments. Among these materials, GdFe3(BO3)4 has the most complex phase diagram as suggested by previous studies. [1,2] These studies suggest that iron moments order antiferromagnetically below T$_{N}\sim $36 K and that there are several additional magnetic phase transitions below T$_{N}$. Yet whether and at what temperature the Gd moments order and the nature of the additional transitions, remain largely unknown. Using x-ray magnetic scattering, we have verified that the moments order antiferromagnetically with a propagation vector (0 0 3/2). Large resonant scattering enhancements at the Gd L$_{II}$ and L$_{III}$ edges show unambiguously that Gd moments order at T$_{N}$. Both resonant and nonresonant scattering data exhibit a splitting of the magnetic peak along c* above $\sim $ 10 K which indicates an incommensurate phase transition, with the incommensurability $\delta $ increasing continuously as a function of temperature ($\delta \sim $.0038 near T$_{N})$. Use of the NSLS/BNL is supported by the U. S. DOE under Contract no. DE-AC02-98CH10886. [1] F. Yen et. al, PRB 73, 54435 (2006) [2] A. I. Pankrats et. al, JETP 99, 766 (2004)