Berlin 2024 – scientific programme

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MA: Fachverband Magnetismus

MA 46: Poster II

MA 46.48: Poster

Thursday, March 21, 2024, 15:00–18:00, Poster C

Disentangling the ferrimagnetic moment arrangement in the Ti-doped Barium hexaferrite using EMCD — •Hitoshi Makino¹, Rolf Erni², Bernd Rellinghaus¹, and Darius Pohl¹ — ¹DCN, cfaed, TUD Dresden University of Technology, Germany — ²Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendolf, Switzerland

Barium hexaferrite is a well-known ferrimagnetic material with good durability at high temperatures and in erosive environments. Previous research has indicated that small Ti substitutions can enhance the coercivity at elevated temperatures. Our efforts aim at elucidating the underlying mechanism through measurements of electron energy loss magnetic chiral dichroism (EMCD), the electron analog to XMCD. We have deconvolved the Fe L-edges as obtained from classical EMCD measurements into different oxidation states of iron and estimated the influence of Ti substitution on the magnetic moments on each iron site. From this analysis, we identified that Ti2+ is substituted to the 4f2 site where Fe has an antiparallel magnetic moment in the Fe2+ octahedral oxidation state. However, EMCD signal of Fe2+ indicate parallel magnetic moment. EMCD measurements utilizing electron vortex beams (EVBs) in an aberration-corrected STEM hold the promise of achieving atomically resolved mappings of the magnetic moment. However, low signal-to-noise ratios (SNRs) currently impede atomic resolution in such measurements. Therefore, we have conducted EVB-EMCD measurements at the atomic scale using a direct detection camera. The impact on the method and achievable resolution will be discussed.

Keywords: EMCD; electron vortex beam; EELS; barium hexaferrite; ferrimagnetism