Dr. Maria Cristina Bartha (Project Director)

Dr. Victor Kuncser

Dr. Petre Badica

Dr. Cezar Comanescu

Dr. Alina Crisan

Dr. Andrei Kuncser

Dr. Mihai Alexandru Grigoroscuta

Ph.D Student Andrei Alexandru-Dinu

MSc. Student  Ani Sergentu

Stage I summary:

In this first stage of the project, oxide precursor nanopulbers with garnet structure of RE3Fe5O12 type were prepared, where RE= Gd, Tb, Dy and Ho  and were complexly characterized both from a structural and morphological point of view. In order to obtain the materials, two processing methods were used (one of them being used for the first time on this type of compounds). At the same time, several studies related to the evolution of properties have been carried out, at this stage, the emphasis being placed on the magnetic properties of oxides with garnet structure obtained by the classical method.

Stage II summary:

The second stage of the experimental demonstration project  aimed at obtaining bulks with garnet structure of RE3Fe5O12, where RE = Gd, Tb, Dy and Ho  by the Spark Plasma Sintering method and their complex structural and microstructural characterization and the investigation of magnetic properties. The SPS method allows to perform sintering heat treatments at high temperatures (up to 2400 °C) using high heating and/or cooling rates (up to 500 °C/min). Among the advantages of using this method are: obtaining bulks with high density (more than 90% of the theoretical density of the processed material), maintaining low particle sizes due to the rapidity of the heat treatment, obtaining microstructural characteristics superior to those obtained by classical sintering treatments, etc. The structural and microstructural investigation of the materials reveals two phases with garnet structure: a stoichiometric phase of  (Gd3(Feoct+tet)5O12) type which is the majority (≥ 90%), in some of the samples it is even the only phase, and a phase showing cationic and/or oxygen stoichiometric defects of the  (Gd)3-x[(Fe2-x)oct(Fe3-x)tet]O12-x type. The coexistence of the two phases significantly influences the properties, especially the magnetic properties which are extremely sensitive to the local changes involving cation distribution and/or defects generated by the variation of oxygen stoichiometry. Therefore, the obtained materials show a distribution of magnetic couplings favoring the achievement of properties with varied application potential. These will be explored in the final stage of the project, the aim being to select demonstrator material with optimal properties for the proposed applications. In addition, some studies on the switching properties of the selected material have been carried out.

Web of Science articles - published or accepted:

1. "Advance of Nanoparticles and Thin Films", Bogdana Borca and Cristina Bartha, Coatings 2022, 12(8), 1138; https://doi.org/10.3390/coatings12081138
2. "Kinetics and the Effect of Thermal Treatments on the Martensitic Transformation and Magnetic Properties in Ni₄₉Mn₃₂Ga₁₉ Ferromagnetic Shape Memory Ribbons", Tolea, F.; Popescu, B.; Bartha, C.; Enculescu, M.; Tolea, M.; Sofronie, M., Magnetochemistry 2023, 9, 7. https://doi.org/10.3390/magnetochemistry9010007.
3. "Up-Conversion Luminescence and Magnetic Properties of Multifunctional Er³⁺/Yb³⁺-Doped SiO₂-GdF₃/LiGdF₄ Glass Ceramics", Secu, C.; Bartha, C.; Radu, C.; Secu, M. Magnetochemistry 2023, 9, 11. https://doi.org/10.3390/magnetochemistry9010011.
4. Synthesis of CoFe₂O₄ Through Wet Ferritization Method Using an Aqueous Extract of Eucalyptus Leaves, Gingasu D., Culita DC., Moreno JMC., Marinescu G., Bartha C., Oprea O.,Preda S., Chifiriuc MC., Popa M., Coatings 2023, 13(7), 1250; https://doi.org/10.3390/coatings13071250.

International Conferences:

1. Cristina Bartha, Andrei Alexandru Dinu, Cezar Comanescu, Simona Greculeasa, Nicusor Iacob, Aurel Leca, and Petre Badica, "Rare earth garnet of Gd3Fe5O12 type for future generation of electronic devices", 7^th edition of the International Workshop Of Materials Physics, Recent Trends in Magnetism and Superconductivity, 31 of August- 2 of September, Magurele, 2022 ( poster ).
   
2. Structural, Mössbauer Spectroscopy and Magnetic Investigations of Gd₃Fe₅O₁₂ garnets obtained by different routes”, C. Bartha,  C. Comanescu, M. Grigoroscuta, A. Alexandru-Dinu, P. Badica and V. Kuncser, International Conference on the Applications of the Mössbauer Effect -ICAME 2023, 3- 9 Septembrie 2023, Cartagena de Indias, Columbia (Oral presentation).
3. Magnetic Properties of Rare Earth Iron Garnets Prepared by Two Synthesis Routes”, A. Alexandru-Dinu, C. Bartha, M. Grigoroscuta, C. Comanescu, V. Kuncser and P. Badica, 8th  International Conference on Superconductivity and Magnetism,  4-11 Mai 2023, Ölüdeniz-Fethiye Turcia (Poster).
4. Magnetic Oxide Ceramics for Spintronics Applications” C. Bartha, A. Alexandru-Dinu, M. Grigoroscuta, C. Comanescu and P. Badica, 8th  International Conference on Superconductivity and Magnetism,  4-11 Mai 2023, Ölüdeniz-Fethiye Turcia (Poster).
5. Bulk MgB₂ and Rare Earth Iron Garnets Processed by Spark Plasma Sintering”, P. Badica, 8th  International Conference on Superconductivity and Magnetism,  4-11 Mai 2023, Ölüdeniz-Fethiye Turcia (Oral presentation).

Patent

"Process for obtaining oxide materials with garnet structure based on iron and rare earths and types of systems obtained, application no A/00200 din 25/04/2023  submitted to OSIM.

Maria Cristina Bartha (Valsangiacom), PhD in Physics

Senior Researcher II

Telephone: +40-(0)21-2418 146

Department: Magnetism and Superconductivity

Email: cristina.bartha@infim.ro