A versatile X-ray phase retarder for lock-in XMCD measurements

Author(s)

Poldi, Eduardo H. T. ; Escanhoela Jr, Carlos A. ; Fonseca Jr, Jairo ; Eleoterio, Marcos A. S. ; dos Reis, Ricardo D. ; Lang, Jonathan C. ; Haskel, Daniel ; Souza-Neto, Narcizo M.

• Document type: Journal article
• Source: JOURNAL OF SYNCHROTRON RADIATION; v. 27, p. 7-pg., 2020-09-01.

Abstract

X-ray magnetic circular dichroism (XMCD) is a technique commonly used to probe magnetic properties of materials with element and orbital selectivity, which requires the use of circularly polarized (CP) X-rays. It is possible to accomplish XMCD experiments with fixed CP and alternating the magnetic field orientation, but most reliable data are obtained when alternating the magnetization orientation and the polarization between right and left helicities. A versatile strategy has been developed to perform XMCD experiments using a hard X-ray quarter-wave plate, at both polychromatic dispersive and conventional monochromatic optics, in combination with synchronous data acquisition. The switching frequency waveform is fed into a lock-in amplifier to detect and amplify the XMCD signal. The results on a reference sample demonstrate an improvement in data quality and acquisition time. The instrumentation successfully generated 98% of CP X-rays switching the beam helicity at 13 Hz, with the possibility of faster helicity switching once it is installed at the new Brazilian fourth-generation source, SIRIUS. (AU)

• FAPESP's process: 14/26620-8 - X-ray 1/4 wave plate for magnetic dichroism
• Grantee: Eduardo Henrique de Toledo Poldi
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 14/05480-3 - Multi-user equipment approved in grant 2013/22436-5: facility for high pressure experiments
• Grantee: Narcizo Marques de Souza Neto
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 14/26450-5 - ORBITAL MAGNETISM IN DOUBLE PEROVSKITE COMPOUNDS UNDER EXTREME CONDITIONS BY SYNCHROTRON RADIATION TECHNIQUES
• Grantee: Carlos Augusto Escanhoela Júnior
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/22436-5 - Synchrotron Radiation techniques under extreme conditions
• Grantee: Narcizo Marques de Souza Neto
• Support Opportunities: Research Grants - Young Investigators Grants