Karel Závěta was an important figure in condensed matter physics. 67 years ago, on the first of February 1956, he joined the then Institute of Technical Physics of the Czechoslovak Academy of Sciences, today called the Institute of Physics of the Czech Academy of Sciences. He began his scientific career in the Department of Magnetism led by J. Brož. He became involved in the study of ferrites and continued in this area in cooperation with S. Krupička. The topic of his doctoral thesis was the use of electric conductivity to measure the magnetocaloric effect. For several years he held the post of the Science Secretary of the institute.
Karel Závěta was an important figure in condensed matter physics. 67 years ago, on the first of February 1956, he joined the then Institute of Technical Physics of the Czechoslovak Academy of Sciences, today called the Institute of Physics of the Czech Academy of Sciences. He began his scientific career in the Department of Magnetism led by J. Brož. He became involved in the study of ferrites and continued in this area in cooperation with S. Krupička. The topic of his doctoral thesis was the use of electric conductivity to measure the magnetocaloric effect. For several years he held the post of the Science Secretary of the institute.
During a six-month internship in the group of K. P. Bělov at the Moscow State University, he focused on the physical properties of ferrite single crystals and returned to the already renamed Institute of Solid State Physics. In the 1960s, in collaboration with the group of E. Trinkler of the Latvian Academy of Sciences in Riga, he studied the effect of gamma radiation on the magnetic properties of ferrites. He lectured on magnetic properties of solids at the Faculty of Mathematics and Physics of Charles University. In 1968 and 1969, he was a visiting professor at the University of Maryland, where he continued his research on the properties of ferrites using ferromagnetic resonance. He gave semester lectures on selected problems of magnetism of solids and a number of invited lectures at prestigious American universities.
After his return from the USA, as a result of normalisation, his contacts with foreign scientists were restricted and he was not allowed to travel abroad on business. In collaboration with J. Šesták, he began to work on amorphous magnetic materials prepared as rapidly cooled glass containing iron oxide. He established collaboration with J. Schneider's group in Dresden on the research into amorphous materials, which in the 1970s was extended to the study of the properties of magnetic metallic glass in the form of thin strips prepared in P. Duhaj's group at the Institute of Physics of the Slovak Academy of Sciences.
The successful results of the research into amorphous materials in collaboration with the Dresden group were rewarded in 1982 with a joint prize of the Czechoslovak Academy of Sciences and AdW GDR. Since the beginning of the 1980s at the Institute of Physics in collaboration with K. Jurek’s group, K. Závěta worked on the magnetic domain structure of amorphous ribbons using scanning electron microscopy. A little later he established a close and fruitful collaboration with T. Zemčík from the Institute of Physics of Materials of the Czechoslovak Academy of Sciences in Brno, when they started to investigate magnetically ordered amorphous substances using Mössbauer spectroscopy.
After the death of T. Zemčík in 1993, he became the head of the Mössbauer Spectroscopy Laboratory as a joint department of the Faculty of Mathematics and Physics of Charles University, the Institute of Physics, Faculty of Science of Charles University and the Institute of Inorganic Chemistry of the Czech Academy of Sciences in the premises of the Faculty of Mathematics and Physics of Charles University in Troja and was its head until 2009. He contributed to the development of the study of magnetic materials, especially magnetic nanoparticles and later multiferroic materials using a combination of measurements of their magnetic properties and Mössbauer spectroscopy.
His close collaboration with E. Pollert and later with O. Kaman and V. Herynek, with whom he worked on magnetic iron oxide nanoparticles and their medical applications for hyperthermia in cancer treatment and as contrast agents for nuclear magnetic resonance imaging, proved to be very fruitful. In addition, K. Závěta, in collaboration with the J. Heyrovsky Institute of Physical Chemistry, was engaged in a comprehensive research of the catalytic properties of iron-incorporated zeolites. During his tenure at the Department of Low Temperature Physics of the Faculty of Mathematics and Physics of Charles University he was a supervisor or consultant for a number of Bachelor, Master and Doctoral theses and lectured on Mössbauer spectroscopy and magnetic nanoparticles in the Master and Doctoral programmes.
In 2008-2011, Karel Závěta was the co-investigator of the "Czech Scientists in Exile 1948-1989" grant, for which the research team was awarded the Award of the Czech Academy of Sciences. He was the editor of the proceedings of a number of conferences, member of the editorial board of the Czechoslovak Journal of Physics. For many years he has been involved in organizing the Soft Magnetic Materials conference series as a member of the organizing committees. In 2018 he still lectured, as he himself had repeatedly said in several of his previous presentations, at his "last conference", specially organized on the occasion of his significant life anniversary – Mössbauer Spectroscopy in Materials Science 2018 at Villa Lanna in Prague. He lived up to his favourite quote by A. Maurois: "Growing old is no more than a bad habit which a busy person has no time to form.”
He devoted himself to a rich and varied scientific activity until the last moment. Last year, together with his son-in-law, P. Ripka, he edited and reviewed the second edition of the book "Magnetic Sensors and Magnetometers". It is also a pleasure to remember "Kája Závěta" (no one who knew him closely would probably refer to him differently) as one of the last gentlemen in physics, with a great variety of elegant bow ties under his neck. He was a gentleman not only in his appearance, but mainly in his sensitive approach to all his colleagues, his gallantry towards women and his willingness to discuss any problem. As a connoisseur and lover of classical music, he liked to attend concerts, adorned with his typical bow tie with a musical note motif. He was proud of his extended family, which he loved and about which he regularly gave his friends an extensive New Year's "Report". He was one of those who, without undue mentoring, managed to positively influence those around him by personal example, and for this reason our Kája will be remembered fondly and for a long time.
Karel Závěta passed away at the age of ninety on February 1, 2023.