Short-Range and Long-Range Order in AFM–FM Exchange Coupled Compound LiCu2(VO4)(OH)2

We performed a 31 P NMR study of the metallic iron phosphide FeP in zero external magnetic field, as well as by sweeping the externally applied magnetic field H both on powder and single crystalline samples at several fixed frequencies. It was the main goal of our work to determine and explore the field dependent transformation of the magnetically ordered helical structure in FeP: the zero-field NMR spectrum for the polycrystalline sample can be easily explained assuming an incommensurate spiral ordering of Fe magnetic moments with a dominating contribution to the local field at the phosphorus nucleus from the Fe-31 P transferred hyperfine interactions. The components of the transferred hyperfine-interaction tensor were evaluated within a straightforward model approach. The NMR lineshape of the powdered FeP sample gradually changes with increasing field from the trapezoidal-like shape at low fields to a pronounced asymmetric double-horn shape at highest field. The former is typically obtained for powdered samples in applied magnetic fields while the latter is characteristic for the NMR spectra of non-magnetic atoms in single-crystalline helimagnets. The observed transformation of our 31 P NMR spectra of FeP provides strong evidence of the spin-reorientation of the spin-flop type in FeP which occurs in the range of strong external fields 4 < µ0H < 5 T confirmed also by specific-heat measurements. The line pattern of the single-crystal 31 P NMR spectra for external magnetic fields directed within the (ac)-plane exhibit a pronounced four-peak structure characteristic of an incommensurate helimagnetic ground state with two pairs of magnetically inequivalent phosphorus positions. These spectra were successfully simulated assuming a simple planar helix of Fe magnetic moments in the (ab)-plane with a phase shift of 36 degrees between Fe1-Fe3 and Fe2-Fe4 sites according to data from neutron scattering. Rotational single crystal field-sweep NMR experiments were performed both below and above the spin-reorientation transition field at fixed frequencies of νLarmor (31 P) = 33 MHz and 140 MHz, respectively. Theoretical estimations of the transferred hyperfine coupling provide an excellent quantitative description of the observed angular dependences for the experimentally determined field separations between the resonance fields of 31 P in magnetically ordered FeP and the resonance field of free Larmor precession, which serves as the diamagnetic reference field. Rotational single-crystal NMR experiments in high fields reveal an effect of varying phosphorous local fields distribution caused by an iron spin-reorientation transition in high magnetic field.

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“…Here ψ is the angle between external and local fields, E is the energy constant. Following Boltzman-like distribution one obtains 25 :…”

Section: Field-sweep 31 P Nmr Of the Fep Powder Samplementioning

confidence: 99%

NMR Analysis of the Magnetic Structure and Hyperfine Interactions in a FeP Binary Helimagnetic

et al. 2019

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NMR study of magnetic structure and hyperfine interactions in the binary helimagnet FeP

et al. 2020

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Electronic structure and microscopic model of Cu$$_{2}$$(SeO$$_{3}$$)F$$_{2}$$: a 2-D AFM ladder compound

Iqbal

Rahaman

2023

Eur. Phys. J. B

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Short-Range and Long-Range Order in AFM–FM Exchange Coupled Compound LiCu₂(VO₄)(OH)₂

Cited by 3 publications

References 24 publications

NMR Analysis of the Magnetic Structure and Hyperfine Interactions in a FeP Binary Helimagnetic

NMR Analysis of the Magnetic Structure and Hyperfine Interactions in a FeP Binary Helimagnetic

NMR study of magnetic structure and hyperfine interactions in the binary helimagnet FeP

Electronic structure and microscopic model of Cu$$_{2}$$(SeO$$_{3}$$)F$$_{2}$$: a 2-D AFM ladder compound

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