Doping effects of Cr on the physical properties of BaFe1.9−xNi0.1CrxAs2

Abstract

We present a systematic study on the heavily Cr doped iron pnictides BaFe1.9−xNi0.1CrxAs2 by using elastic neutron scattering, high-resolution synchrotron X-ray diffraction (XRD), resistivity and Hall transport measurements. When the Cr concentration increases from x = 0 to 0.8, neutron diffraction experiments suggest that the collinear antiferromagnetism persists in the whole doping range, where the Néel temperature TN coincides with the tetragonal-to-orthorhombic structural transition temperature Ts, and both of them keeps around 35 K. The magnetic ordered moment, on the other hand, increases within increasing x until x = 0.5, and then decreases with further increasing x. Detailed refinement of the powder XRD patterns reveals that the Cr substitutions actually stretch the FeAs4 tetrahedron along the c−axis and lift the arsenic height away Fe-Fe plane. Transport results indicate that the charge carriers become more localized upon Cr doping, then changes from electron-type to hole-type around x = 0.5. Our results suggest that the ordered moment and the ordered temperature of static magnetism in iron pnictides can be decoupled and tuned separately by chemical doping.

Evolution of superconductivity and antiferromagnetic order in Ba(Fe$_{0.92-x}$Co$_{0.08}$V$_x$)$_2$As$_2$

“…As shown in Fig. 3(c), the ordered magnetic moments of Ba(Fe 0.92−x Co 0.08 V x ) 2 As 2 exhibit a strong dome-like doping dependent behavior with maximum value of 0.29µ B , similar evolution of moments was also reported recently in Crdoped BaFe 1.9−x Ni 0.1 Cr x As 2 [18].…”

“…3(c)). The similar recoveries of magnetic phase have been observed in Cr-doped BaFe 1.9−x Ni 0.1 As 2 [18] and K-doped BaFe 2−x Co x As 2 [19], which seems to be a universal phenomenon in FeAs-122 system but has never been realized in other unconventional magnetic superconducting system as far as we know. In our previous work [11], V is shown to act as an effective hole dopant similar as the cases of Cr and K. So a straightforward explanation about the recovery of magnetic order could be based on the Fermi surface nesting picture.…”

“…For the tetragonal to orthorhombic structural transition, the neutron extinction effect from the peak splitting results in a significant change for the peak intensity of (2 0 2) around the transition temperature. However, for x≥0.24, the huge structural factor and strong intensity of the Bragg peaks make it difficult to figure out the structural transition via extinction effect [18]. The structural transition temperatures T S are roughly determined from the maximum slope of the change of (2 0 2) intensity as shown in Fig.…”

Spin excitations and spin wave gap in the ferromagnetic Weyl semimetal Co3Sn2S2

“…The integrated intensity of the (1, 0, 1) peak reveals a clear ferromagnetic transition at T C = 175 K, consistent with the magnetization results (Figure 1(f)). The ordered moment M can be estimated by comparing the intensities associated with magnetic scattering and nuclear scattering [45] (See Supplemental Materials). A value of 0.28±0.02 µ B per Co atom at the base temperature of T =8 K was obtained.…”

Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with Spin-Vortex Crystal Order

“…x , σ SF y , and σ SF z , which is only sensitive to the magnetic excitations/moments that are perpendicular to Q [26][27][28][29][30][31][32][33][34][35][36][37][38]. The measured intensity is related to the magnetic form factor F (Q) (or structural factor f M (Q)) and orientation of ordered moments, it can be also affected by the instrument resolution and higher-harmonic scattering from the monochromator [47,65,66]. After considering the geometries of lattice and polarization at two unparallel but equivalent wavevectors, we can separate all three magnetic excitation components: M a , M b , and M c along the lattice axes a M , b M , and c, respectively [23,29,32,38,46,47].…”