Magnetism of pure iron jarosites

Single-crystal X-ray diffraction study of synthetic sodium–hydronium jarosite

“…The room-temperature structure was solved in space group R3m using direct methods. The space group choice R3m (R int = 0.034) is in agreement with previous single-crystal studies of Na jarosite and H 3 O jarosite (Grohol et al 2003;Nestola et al 2013;Majzlan et al 2004;Plášil et al 2014;Spratt et al 2014).…”

Octupolar ordering of classical kagome antiferromagnets in two and three dimensions

“…The energy integrated neutron scattering cross-section is proportional to the instantaneous spin correlator (16) and provides an experimental tool for its measurement. Previous numerical works on the kagome antiferromagnet have considered only the powder averaged structure factor.…”

Determination of the single-ion anisotropy energy in aS=52kagome antiferromagnet using x-ray absorption spectroscopy

“…The D 4h symmetry of the ligand field was lowered to C 2 to model the actual positions of the oxygen anions around the cation, as obtained from crystallographical data. 11,17 However, this had no effect on the agreement of the calculated spectra with experiment nor on the values as listed in Table I, and hence we consider an estimate for E xy from our data presently not attainable. It should in this respect be noted that the value for D z was found to change with the splitting of the main peak at 709 meV introduced by the trigonal distortion of the ligand field.…”

“…Potassium iron jarosite is representative for most of the iron analogs. In this system a transition to a noncollinear long-range-ordered state is observed at 64 K despite that the magnitude of the Curie-Weiss temperature ⌰ CW is as high as −800 K. 11,17 The ground state has shown to be a so-called q = 0 state of positive chirality, in which the spins lie within the kagome plane and all point either in or out of each shared kagome triangle. 9,12,13,18,19 The large figure ⌰ CW / T N = 12.5 is an indication of relatively strong geometric frustration, 20 but clearly the observed longrange-ordered ground state points to additional terms in the Hamiltonian of this kagome antiferromagnet beyond nearneighbor exchange.…”

“…10 It has been suggested that the spin-glass state is the result of proton transfer from the hydronium groups to the Fe-͑O eq H͒-Fe superexchange mediating hydroxy groups. 17 One indication that this could happen might be that the OH groups at the crystallographically analogous location in the related kagome compound zinc paratacamite can form a muonium state by chemically binding a positive muon. 27 The aim of the work described here is to investigate the origins of the magnetic anisotropy ͑of either single-ion or DMI character͒ in the iron jarosites and to understand the essential differences between the salts, such as potassium jarosite, with a long-range-ordered ground state and hydronium jarosite.…”