Investigation of Helimagnetism in Dy and Ho Thin Films by Neutron Reflectometry

In this paper, the results of investigating thin films of rare-earth helimagnetics (REMs) Dy and Ho by polarized neutron reflectometry are presented. It is shown that the growth by magnetron sputtering of rare-earth structures on sapphire substrates with a buffer layer Nb $$\left[ {1\bar {1}02} \right]$$ Al2O3||[110]Nb|| $$\left[ {0001} \right]R$$ leads to complete relaxation of the Nb crystal lattices and the rare-earth film. It is found that some magnetic phase transitions typical of bulk Dy and Ho are not observed in 200 nm [0001]R thin films or are observed in a modified form. Differences between the Neel and Curie temperatures of thin REM films compared to bulk REMs are determined based on polarized-neutron-reflectometry data and measurements of the temperature dependence of the magnetization in the sample plane.