Effect of external pressure on the magnetic properties of LnFeAsO (Ln = La, Ce, Pr, Sm)

Abstract

We investigate the effect of external pressure on magnetic order in undoped LnFeAsO (Ln = La, Ce, Pr, La) by using muon-spin relaxation measurements and ab-initio calculations. Both magnetic transition temperature T m and Fe magnetic moment decrease with external pressure. The effect is observed to be lanthanide dependent with the strongest response for Ln = La and the weakest for Ln = Sm. The trend is qualitatively in agreement with our DFT calculations. The same calculations allow us to assign a value of 0.68(2) µ B to the Fe moment, obtained from an accurate determination of the muon sites. Our data further show that the magnetic lanthanide order transitions do not follow the simple trend of Fe, possibly as a consequence of the different f -electron overlap. ‡ now at Leibnitz Institute IFW,

Tuning the magnetic and structural phase transitions of PrFeAsO via Fe/Ru spin dilution

“…For the undoped parent PrFeAsO the ZF-µSR time spectra are well fitted with N = 2 and occupancy f 1 ≈ 75% and f 2 ≈ 25%, which reflects the presence of two inequivalent muon sites [15][16][17] . In the x = 0.33 and 0.4 samples, the two frequencies are still detectable, but with f 2 reduced in half.…”

Structural properties and phase diagram of the La(Fe1−xRux)AsO system

“…49,50 For each composition the fit has been applied only to those data points which correspond to temperatures where the sample volume is almost fully magnetic, in order to consider the magnetic response coming from the whole sample. Unfortunately, this procedure cannot be applied for those samples with x > 0.30 which do not display coherent precessions of the muon spin due to the lack of long range magnetism and the behavior of S(T) cannot be inspected.…”

Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting Ca La1−Ba1.75−La0.25+Cu3O system

“…Indeed, recently it has been argued that electronic inhomogeneity controlled by organization of defects, lattice distortions, interface states, nanoscale phase separation in the layered oxides has substantial influence in the superconducting properties of cuprates [4][5][6][7][8][9]. This appears to be common to all layered superconductors as diborides [10][11][12][13] and more recently pnictides [14][15][16][17][18][19]. Here it should be specified that large structural differences from one cuprate family to another one hinders the investigation of what drives the T c max in these materials.…”