Magnetic and specific heat properties of YFe3(BO3)4 and ErFe3(BO3)4.

The present paper reports on the specific heat and magnetization of the YFe(3)(BO(3))(4) and ErFe(3)(BO(3))(4) single crystals. In both compounds, antiferromagnetic order of the iron spins evolves at T(N) = 38 K. The experimental data suggest that the magnetic moments are in the basal plane of the trigonal crystal for both compounds. In the magnetically ordered state the crystal is subdivided into three types of domains, the magnetic moments of the Fe(3+) ions being aligned along the a axis within each domain. For ErFe(3)(BO(3))(4), two non-equivalent magnetic positions of the Er(3+) ions in each domain are observed.