Magnetic structures and interplay between rare-earth Ce and Fe magnetism in single-crystal CeFeAsO

Abstract

Neutron and synchrotron resonant x-ray magnetic scattering (RXMS) complemented by heat capacity and resistivity measurements reveal the evolution of the magnetic structures of Fe and Ce sublattices in a CeFeAsO single crystal. The RXMS of magnetic reflections at the Ce L-II edge shows a magnetic transition that is specific to the Ce antiferromagnetic long-range ordering at T-Ce approximate to 4 K with short-range Ce ordering above T-Ce, whereas neutron diffraction measurements of a few magnetic reflections indicate a transition at T* approximate to 12 K with an unusual order parameter. Detailed order-parameter measurements on several magnetic reflections by neutrons show a weak anomaly at 4 K that we associate with the Ce ordering. The successive transitions at T-Ce and T* can also be clearly identified by two anomalies in heat capacity and resistivity measurements. The higher transition temperature at T* approximate to 12 K is mainly ascribed to Fe spin reorientation transition, below which Fe spins rotate uniformly and gradually in the ab plane. The Fe spin reorientation transition and short-range Ce ordering above T-Ce reflect the strong FeCe couplings prior to long-range ordering of the Ce. The evolution of the intricate magnetic structures in CeFeAsO going through T* and T-Ce is proposed. Neutron and synchrotron resonant x-ray magnetic scattering (RXMS) complemented by heat capacity and resistivity measurements reveal the evolution of the magnetic structures of Fe and Ce sublattices in a CeFeAsO single crystal. The RXMS of magnetic reflections at the Ce L II edge shows a magnetic transition that is specific to the Ce antiferromagnetic long-range ordering at T Ce ≈ 4 K with short-range Ce ordering above T Ce , whereas neutron diffraction measurements of a few magnetic reflections indicate a transition at T * ≈ 12 K with an unusual order parameter. Detailed order-parameter measurements on several magnetic reflections by neutrons show a weak anomaly at 4 K that we associate with the Ce ordering. The successive transitions at T Ce and T * can also be clearly identified by two anomalies in heat capacity and resistivity measurements. The higher transition temperature at T * ≈ 12 K is mainly ascribed to Fe spin reorientation transition, below which Fe spins rotate uniformly and gradually in the ab plane. The Fe spin reorientation transition and short-range Ce ordering above T Ce reflect the strong Fe-Ce couplings prior to long-range ordering of the Ce. The evolution of the intricate magnetic structures in CeFeAsO going through T * and T Ce is proposed. Disciplines Condensed Matter Physics | Materials Science and Engineering | Metallurgy Comments

Spin reorientation and Ce-Mn coupling in antiferromagnetic oxypnictide CeMnAsO

“…This is different from the itinerant CeFeAsO with a much lower ordered Fe moment of ∼ 0.9µ B compared to the 4 µ B expected from a localized moment 8 . The inplane checker-board-like AFM structure of the C-type order in CeMnAsO in T < T N suggests that the NN interaction J 1 is dominant whereas inplane nextnearest-neighbor (NNN) interaction J 2 is very weak or negligible.…”

“…1. Similar to the tetragonal structure in RFeAsO (R is rare earth element) 8 or LaMnAsO 14 , the structure of CeMnAsO consists of MnAs and CeO layers where the Mn…”

Structural and magnetic characterization of iron oxyselenidesCe2O2Fe2OSe2andMcCabe1, Wills2, Chapon3 et al. 2014Phys. Rev. B139260View full textAdd to dashboardCite

“…We find no evidence of Fe moment reorientation at the onset of Ce 3+ moment ordering in Ce 2 O 2 Fe 2 OSe 2 (which we expect our analysis to be sensitive to, given the relatively large moments on Fe sites). This is in contrast to CeMnAsO [14] and CeFeAsO [13], where some reorientation of transition metal spins has been reported at T N,Ce . The lack of any spin reorientation in Ce 2 O 2 Fe 2 OSe 2 may reflect the Ising-like nature of the Fe ordering, with the local anisotropy of Fe directing moments oriented along Fe-O(2) bonds and parallel to the expected Ce easy axis.…”

“…Although the superconductivity arises in the iron arsenide layers, the Ln 3+ cation has a significant role in both tuning the superconducting T c in the doped materials [1,4] and in defining the magnetism of the parent nonsuperconducting materials (such as the spin reorientations in NdFeAsO [5] and PrFeAsO [6]). This has led to much research into the interplay between transition metal and lanthanide magnetic sublattices in these and related mixed-anion systems [7][8][9][10][11][12][13][14][15][16][17][18][19] [23] and a collinear model [10,22]. Recent work suggests that the 2-k model is the more likely [24][25][26].…”

Magnetism of theFe2+andCe3+sublattices inCe2<

“…For example, the Fe 2+ moments of CeFeAsO order antiferromagnetically in the ab plane at T N,Fe = 140 K [25] while the Ce 3+ moments couple strongly with the Fe 2+ moments at relatively high temperatures [30], before developing a long range order below ∼3.7 K with moments predominantly in the ab plane [25]. Recent studies suggested some reorientation of the Fe moments within the ab plane at the onset of the long range order of the Ce moments [31]. The Ce 3+ ions influence the iron magnetic sublattice, and can also induce exotic properties such as Kondo screening of the local moment in closely-related CeFePO [32] and CeRuPO [33].…”