Interplay between magnetism and superconductivity in HoNi2B 2C revisited

Abstract

In this work the magnetic and superconducting properties of HoNi 2B2C were investigated by using powder neutron diffraction and the specific heat and upper critical field (Hc2) measurements as a function of temperature. Below T = 8 K, three distinct anomalies at the temperatures TN = 5.2 K, Tm =5.6 K and TM = 6.0K were observed in the specific heat of HoNi2B2C, as reported in the literature. Our neutron data confirm the transitions to the Néel structure (qN = c*) at TN and to the modulated structure (qM = 0.586a*) at TM. The peak at T H1 = 5.7 K in the specific heat data, whose exact nature was not known hitherto, is now attributed to the onset of a qH1 = 0.905c* magnetic helical structure as seen in our neutron data. Comparison between the thermal evolution of the magnetic structures and the temperature dependence of the upper critical field confirms that the first Hc2(T) depression at 6.1 K arises from the qM = 0.586a* modulated magnetic structure. The second depression in Hc2(T) below 5.7 K can be ascribed to the qm = 0.905c* magnetic helical structure. © IOP Publishing Ltd and Deutsche Physikalische Gesellschan.