Effects of Co substitution on the structural and magnetic properties of Sr ( Ni 1 - x Co x ) 2 P 2

Journal Article · 09 November 2023 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.108.174415 · OSTI ID:2222449

Schmidt, J.  ^[1]; Gorgen-Lesseux, G. ^[1]; Ribeiro, R. A. ^[1]; Bud'ko, S. L.  ^[1]; Canfield, P. C.  ^[1]

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1. Ames Lab., and Iowa State Univ., Ames, IA (United States)

Although SrNi₂P₂ adopts the common ThCr₂Si₂ structure for T ≥ 325 K, being in an uncollapsed tetragonal state rather than a collapsed tetragonal version, it is a special case for the ThCr₂Si₂ class: on cooling below 325 K it adopts a one-third collapsed orthorhombic phase where one out of every three P rows bonds across the Sr layers. On the other hand, SrCo₂P₂ only exhibits the uncollapsed ThCr₂Si₂ structure from room temperature down to 1.8 K. Regardless of their low-temperature structures, neither SrNi₂P₂ nor SrCo₂P₂ manifests magnetic transitions down to 50 mK and 2 K, respectively. In this work we report the effects of Co substitution in Sr(Ni_{1 - x}Co_x)₂P₂, which allows for tuning the transition between the one-third collapsed and the uncollapsed structure. We find a rapid decrease of the one-third collapsed structural transition temperature with increasing Co fraction, until reaching full suppression for x ≥ 0.1. Substitution levels in the range 0.11 ≤ x ≤ 0.58 show no signs of any transition down to 1.8 K in the magnetization or resistance measurements in the range 1.8 ≤ T ≤ 300 K. However, different magnetically ordered states emerge for x ≥ 0.65, and disappear for x ≥ 0.99, recovering the known paramagnetic properties of the parent compound SrCo₂P₂. Further, these results are summarized in a phase diagram, built upon the characterization by energy dispersive x-ray spectroscopy, x-ray diffraction, temperature-dependent resistance, and field- and temperature-dependent magnetization measurements done on single crystals with different Co fraction. Both the magnetic and structural properties are compared to other systems with ThCr₂Si₂ structure that exhibit magnetic ordering and collapsed tetragonal transitions. The magnetic ordering and moment formation are well described by Takahashi's spin fluctuation theory of itinerant electron magnetism.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); USDOE
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 2222449
• Alternate ID(s): OSTI ID: 2205370
• Report Number(s): IS-J-11,209; TRN: US2407105
• Journal Information: Physical Review. B, Vol. 108, Issue 17; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English