Lattice collapse and the magnetic phase diagram ofSr1−xCaxCo2P2

Abstract

We report that the 122 type Sr1−xCaxCo2P2 solid solution undergoes an anomalous structural transition from the uncollapsed to the collapsed ThCr2Si2 structure at a distinct onset composition near x = 0.5. Correlated with the structural changes, the electronic system evolves from a nearly ferromagnetic Fermi liquid to an antiferromagnetic metal, through a complex crossover regime. The structural collapse, driven by P-P bonding across the (Sr,Ca) layers, is much more pronounced in this system than it is in the analogous Fe-based system, indicating a strong sensitivity of structure to total electron count in the transition metal pnictide 122 family.

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

“…1(b). The magnetic properties of the low Sr doping were studied in [12] and a similar structural evolution was reported for (Ca,Sr)Co 2 P 2 [17]. In this paper, we report on Ca 0.8 Sr 0.2 (c=10.82Å) and Ca 0.6 Sr 0.4 (c=11.41Å).…”

Suppression of magnetic order in CaCo1.86As2 with Fe substitution: Magnetization, neutron diffraction, and x-ray diffraction studies of Ca(CoJayasekara1, Pandey2, Kreyßig3 et al. 2017Phys. Rev. B212410View full textAdd to dashboardCite

“…In this case, the T-cT transition changes both the Co-Co and Co-P-Co bond lengths and also correlates with a transition from a nearly-ferromagnetic Fermi liquid to AFM order. 44 For both compounds, transitions between the magnetically ordered ground states are also tied to changes in the lattice parameters.…”

Anomalous itinerant-electron metamagnetic transition in the layeredSr1−xCaxCo2P2system

“…1. The parameter of c is linearly related to the P-P distance between neighboring Co 2 P 2 layers [7]. In the ucT region of x ≤ 0.5, while a is almost constant, c decreases monotonically with x.…”

“…In the ucT region (x ≤ 0.5) in which the electronic structure is expected to be quasi-2D, the Weiss temperature changes from negative value to 0 K with increasing x, suggesting that Sr 1−x Ca x Co 2 P 2 approaches to a ferromagnetic quantum critical point (QCP). In the cT region (x > 0.5) in which Sr 1−x Ca x Co 2 P 2 shows magnetic orderings [7], the intralayer ferromagnetic moments are coupled antiferromagnetically via layer by layer P-P bondings.…”

“…Since it is known that the structure changes from ucT to cT around x = 0.5 as x increases [7] in the Sr 1−x Ca x Co 2 P 2 system, this system should be one of the ideal systems to control the dimensionality of the magnetic interaction and the itinerancy systematically. The SrCo 2 P 2 with the ucT cell is an enhanced Pauli paramagnetic metal without any magnetic orderings [8].…”