Lattice collapse and quenching of magnetism in CaFe[subscript 2]As[subscript 2] under pressure: A single-crystal neutron and x-ray diffraction investigation

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2009-06, Vol.79 ((2) ; 2009)
• Main Authors: Goldman, A.I., Kreyssig, A., Prokeš, K., Pratt, D.K., Argyriou, D.N., Lynn, J.W., Nandi, S., Kimber, S.A.J., Chen, Y., Lee, Y.B., Samolyuk, G., Leão, J.B., Poulton, S.J., Bud'ko, S.L., Ni, N., Canfield, P.C., Harmon, B.N., McQueeney, R.J.
• Format: Article
• Language: English
• Subjects: ARSENIC COMPOUNDS; CALCIUM COMPOUNDS; DENSITY; DIFFRACTION; FUNCTIONS; HYSTERESIS; IRON; IRON COMPOUNDS; MAGNETIC MOMENTS; MAGNETISM; NEUTRONS; PEAKS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PRESSURE RANGE GIGA PA; QUENCHING; TEMPERATURE RANGE 0273-0400 K; X-RAY DIFFRACTION
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.79.024513

Single-crystal neutron and high-energy x-ray diffraction measurements have identified the phase lines corresponding to transitions among the ambient-pressure paramagnetic tetragonal (T), the antiferromagnetic orthorhombic (O), and the nonmagnetic collapsed tetragonal (cT) phases of CaFe{sub 2}As{sub 2}. We find no evidence of additional structures for pressures of up to 2.5 GPa (at 300 K). Both the T-cT and O-cT transitions exhibit significant hysteresis effects, and we demonstrate that coexistence of the O and cT phases can occur if a nonhydrostatic component of pressure is present. Measurements of the magnetic diffraction peaks show no change in the magnetic structure or ordered moment as a function of pressure in the O phase, and we find no evidence of magnetic ordering in the cT phase. Band-structure calculations show that the transition into the cT phase results in a strong decrease in the iron 3d density of states at the Fermi energy, consistent with a loss of the magnetic moment.