Competing multiple-q magneticstructures in HoGe3: II. Magneticstructures observed in HoGe3

Abstract

The high temperature (HT) and the low temperature (LT)multiple-q vector magnetic structures of the antiferromagneticHoGe3 compound (TN = 11 K) are derived from refinements of high resolution neutron data in terms of Fourieranalysis. Various models are discussed. Over the HT range , T2 = 8.1 K (on heating), the magnetic phase is described with the wavevectors(q1,q2)where q1 = (q1x,0,0) and and , with T dependent length. It corresponds to an amplitude modulated magnetic phase with the moments at an angle of24° (2) with thec axis withinthe plane (b,c). Surprisingly this structure does not square up to a constant moment structure with and or alternatively (2a,b,3c).Instead of locking, the q2 vector jumps at T2 via a first-order transition to a long period structure with an almost 24-times larger cell≈(2a,4b,3c), or in terms of wavevectors to and , which dominates the (LT) range . The (LT) range subdivides into the lock-inLT1 range (T3 = 4.8 K on heating) where the components have a constant length and theLT2 range where q3y andq4y have a lengthvariable with T. In the intermediate temperature range, around the first-orderT2 transition (on heating or cooling), the two structures described with the wavevectors(q1,q2)and (q3, q4) coexist in varying proportions. The most probable LT magnetic structure corresponds toa complex monoclinic multiaxial canted structure with four independent Ho sites as aresult of geometric frustration related to the underlying trigonal prism arrangement of themagnetic atoms with antiferromagnetic interactions.