Electronic structure of Fe and magnetism in the $3d/5d$ double perovskites Ca${}_2$FeReO${}_6$ and Ba${}_2$FeReO${}_6$

Abstract

The Fe electronic structure and magnetism in (i) monoclinic Ca${}_2$FeReO${}_6$ with a metal-insulator transition at $T_{MI}\sim 140$ K and (ii) quasi-cubic half-metallic Ba${}_2$FeReO${}_6$ ceramic double perovskites are probed by soft x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). These materials show distinct Fe $L_{2,3}$ XAS and XMCD spectra, which are primarily associated with their different average Fe oxidation states (close to Fe${}^{3+}$ for Ca${}_2$FeReO${}_6$ and intermediate between Fe${}^{2+}$ and Fe${}^{3+}$ for Ba${}_2$FeReO${}_6$) despite being related by an isoelectronic (Ca${}^{2+}$/Ba${}^{2+}$) substitution. For Ca${}_2$FeReO${}_6$, the powder-averaged Fe spin moment along the field direction ($B=5$ T), as probed by the XMCD experiment, is strongly reduced in comparison with the spontaneous Fe moment previously obtained by neutron diffraction, consistent with a scenario where the magnetic moments are constrained to remain within an easy plane. For $B=1$ T, the unsaturated XMCD signal is reduced below $T_{MI}$ consistent with a magnetic transition to an easy-axis state that further reduces the powder-averaged magnetization in the field direction. For Ba${}_2$FeReO${}_6$, the field-aligned Fe spins are larger than for Ca${}_2$FeReO${}_6$ ($B=5$ T) and the temperature dependence of the Fe magnetic moment is consistent with the magnetic ordering transition at $T_C^{Ba}=305$ K. Our results illustrate the dramatic influence of the specific spin-orbital configuration of Re $5d$ electrons on the Fe $3d$ local magnetism of these Fe/Re double perovskites.

arXiv comment7 pages, 3 figures

References in corpus (20)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Fermi Arcs in a Doped Pseudospin-1/2 Heisenberg Antiferromagnet
• Observation of a $d$-wave gap in electron-doped Sr${}_2$IrO${}_4$
• The Challenge of Spin-Orbit-Tuned Ground States in Iridates
• Electronic structure study of double perovskites $A_2$FeReO${}_6$ (A=Ba,Sr,Ca) and Sr${}_{2}M$MoO${}_6$ (M=Cr,Mn,Fe,Co) by LSDA and LSDA+U
• Spin-orbit coupling in $d^2$ ordered double perovskites
• Signature of high temperature superconductivity in electron doped Sr2IrO4
• Metallic and nonmetallic double perovskites: A case study of A${}_2$FeReO${}_6$ (A= Ca, Sr, Ba)
• Properties of the ferrimagnetic double-perovskite A_{2}FeReO_{6} (A=Ba and Ca)
• Electronic and Magnetic Structures of Sr2FeMoO6
• Electronic structure of half-metallic double perovskites
• Bulk-sensitive photoemission spectroscopy of A_2FeMoO_6 double perovskites (A=Sr, Ba)
• Direct evidence of the orbital contribution to the magnetic moment in AA'FeReO6 double perovskites
• Strong correlation effects of the Re 5$d$ electrons on the metal-insulator transition in Ca${}_2$FeReO${}_6$
• Structural and metal-insulator transitions in rhenium based double perovskites via orbital ordering
• First-order structural transition and pressure-induced lattice/phonon anomalies in Sr${}_2$IrO${}_4$
• Exotic Magnetism and Spin-Orbit Assisted Mott Insulating State in a $3d-5d$ Double Perovskite
• Spin-orbital locked magnetic excitations in a half-metallic double perovskite Ba2FeReO6
• Neutron Scattering Investigation of Rhenium Orbital Ordering in $3d-5d$ Double Perovskite Ca${}_2$FeReO${}_6$

Cited by in corpus (1)

• Magnetic excitations in double perovskite iridates La${}_2$$M$IrO${}_6$ ($M$ = Co, Ni, and Zn) mediated by 3$d$-5$d$ hybridization