Itinerant Ferromagnetism in the As4pConduction Band ofBa0.6K0.4Mn

Abstract

X-ray magnetic circular dichroism (XMCD) measurements on single-crystal and powder samples of Ba0.6K0.4Mn2As2 show that the ferromagnetism below TC ≈ 100 K arises in the As 4p conduction band. No XMCD signal is observed at the Mn x-ray absorption edges. Below TC, however, a clear XMCD signal is found at the As K edge which increases with decreasing temperature. The XMCD signal is absent in data taken with the beam directed parallel to the crystallographic c axis indicating that the orbital magnetic moment lies in the basal plane of the tetragonal lattice. These results show that the previously reported itinerant ferromagnetism is associated with the As 4p conduction band and that distinct local-moment antiferromagnetism and itinerant ferromagnetism with perpendicular easy axes coexist in this compound at low temperature.PACS numbers: 78.70. Dm, 74.70.Xa, 75.50.Cc The search for unconventional superconductivity has resulted in the discovery of materials possessing rich, tunable, physical properties and has been the driving force for much recent theoretical and experimental research [1][2][3][4]. In particular, the high-temperature cuprate and Fe-pnictide superconductors show remarkable coupling between their lattice, charge, and magnetic degrees of freedom, which may be tuned by small alterations to their chemical structures through, for example, electron-or hole-doping by chemical substitution. [5][6][7]. These materials have provided testbeds for Hamiltonians based on the Heisenberg model and their applicability to both local-moment and itinerant magnets [2,[8][9][10]. In particular, the magnetic excitation spectra obtained through inelastic neutron scattering experiments on the parent compounds of the 122-type Fe-pnictide superconductors (AFe 2 As 2 , A = Ba, Sr, Ca) have been described in terms of the J 1 -J 2 Heisenberg model [9,10].Systems related to the 122 Fe-pnictides manifest interesting and exotic material properties. For example, (Ba 1−x K x )(Zn 1−y Mn y ) 2 As 2 is a ferromagnetic semiconductor which may be useful for developing multilayer functional devices [11]. The system studied here, (Ba 0.6 K 0.4 )Mn 2 As 2 , shows local-moment antiferromagnetic (AFM) order below a Néel temperature of T N = 480 K that coexists with halfmetallic itinerant ferromagnetic (FM) order below a Curie temperature of T C ≈ 100 K [6].BaMn 2 As 2 crystallizes in the same body-centered tetragonal ThCr 2 Si 2 lattice (space group I4/mmm) as the parent phases of the superconducting 122 Fe-pnictides [13]. The Gtype (checkerboard-type) AFM insulating ground state of the S = 5 2 Mn spins has an ordered moment of 3.88(4) µ B /Mn below T N = 625(1) K that is directed along the c axis. [1][2][3][4]. It has been demonstrated that BaMn 2 As 2 can be driven from an insulating to metallic ground state upon the substitution of as little as 1.6% K for Ba [18] or by applied pressure [19]. Nevertheless, Ba 1−x K x Mn 2 As 2 retains the G-type Mn local-moment AFM order of its parent insulating compound [3,5,18]. The AFM order is quite r...

Physical properties and electronic structure ofSr2Cr3As2O2containingCrO2Jiang1, Bao2, Zhai3 et al. 2015Phys. Rev. B307530View full textAdd to dashboardCite

“…In particular, the As-4p electrons, with a small fraction near E F , could be spin-polarized. Such a nontrivial scenario was recently found and demonstrated in Ba 1−x K x Mn 2 As 2 which shows weak FM for x >0.19 [58][59][60] . Here the DOS of As-4p also shows a maximum at E F (the inset of Fig.…”

Angle-resolved photoemission observation of Mn-pnictide hybridization and negligible band structure renormalization in BaMn2As2 and BaMn2Sb2Zhang1, Richard2, Roekeghem3 et al. 2016Phys. Rev. B234270View full textAdd to dashboardCite

“…Although it cannot induce the band folding observed in BaMn 2 As 2 , a weak in-plane ferromagnetic component was reported in hole-doped Ba 1−x K x Mn 2 As 2 [22,23]. Although a theoretical study attributes the in-plane ferromagnetic component to a canting of the Mn moments [24], recent X-ray magnetic circular dichroism experiments rather suggest that the ferromagnetic component resides on the As 2p orbital [25]. In either cases, the magnetic structure in BaMn 2 As 2 is certainly prone to a distortion as compared to the simple G-type AFM of the Mn alone, which could possibly induce a band folding.…”

Magnetic hexadecapole order and magnetopiezoelectric metal state in Ba1−xKxMn2As2

“…The X-ray magnetic circular dichroism experiment identified that the ferromagnetic moment arises from the As p orbitals and coexists with the AFM moment of Mn atoms [38]. Although the interplay of the magnetic hexadecapole order and the ferromagnetic order would be an interesting subject, it is left for a future study.…”