Serdecznie zapraszamy na Środowiskowym Seminarium Fizyki Ciała Stałego, które odbędzie się w środę, 28 listopada o godz. 9:00 w sali 1.02A Akademickiego Centrum Materiałów i Nanotechnologii AGH (pawilon D-16) przy ul. Kawiory 30.

The development of new micro and nanomotors design has been of great interest in the recent years due to its potential implementation not only in biological systems for biomedical applications, but also as dynamic and effective platforms to solve environmental issues. Such entities could present autonomous motion under different energy sources, e.g. light, magnetic fields, electric fields, ultrasonic acoustic waves¹ Their design is generally inspired in natural systems, such as kinesin or sperm cells, which not only helped on a better understanding of certain related operating mechanisms and other key features associated to its motion, but also motivated the development of new hybrid motors. Among synthetic motors, catalytic microengines have shown an outstanding progress in the recent years. The development of catalytic engines was initially focused on the fundamental study and potential applications of platinum-based microengines, being not only of great interest the tubular-shape micromotors^2,3 but also the well-known Janus particles⁴, and showing important advances on its future applications in both biomedical⁵ and environmental fields⁶. However, present studies are mainly focused on the development of nano and micromotors moving in presence of non-toxic fuels, which led to the development of interesting novel configurations moving in presence of acid⁷ or water^8,9. Although they present short lifetimes, they open the doors to novel alternative configurations, as for example the research work currently undergoing in our lab based on biocompatible carbonate-based Janus microparticles. It is important to mention the development of hybrid motors based on the rational control of naturally moving species, like sperm, by using magnetic field¹⁰. Such symbiosis is obtained due to the coupling of sperm cells to tubular microjets, and its final configuration is conceived as a potential platform for minimal invasive surgery, diagnosis and drug delivery.

1. Guix M, Mayorga-Martinez CC, Merkoçi A. Chem. Rev. 2014, 114, 6285.
2. Gao W, Sattayasamitsathit S, Uygun A, Pei A, Ponedal A, Wang J. Nanoscale 2012, 4, 2447.
3. Mei YF, Huang GS, Solovev AA, Bermúdez Urena E, Moench I, Ding F, Reindl T, Fu RKY, Chu PK, Schmidt OG. Adv. Mater. 2008, 20, 4085.
4. Ebbens S, Jones RAL, Ryan AJ, Golestanian R, Howse JR. Phys. Rev. E 2010, 82, 015304.
5. Wang J, Gao W. ACS Nano 2012, 6, 5745.
6. Soler L, Sanchez S. Nanoscale 2014, 6, 7175.
7. Gao W, Uygun A, Wang J. J Am. Chem. Soc. 2012, 134, 897.
8. Gao W, Pei A, Wang J. ACS Nano 2012, 6, 8432.
9. Gao W, Feng X, Pei A, Gu Y, Li J, Wang J. Nanoscale 2013, 5, 4696.
10. Magdanz V, Sanchez S, Schmidt OG. Adv. Mater. 2013, 25, 6581.

Serdecznie zapraszamy na Środowiskowym Seminarium Fizyki Ciała Stałego, które odbędzie się w środę, 19 listopada o godz. 9:00 w sali 1.02A Akademickiego Centrum Materiałów i Nanotechnologii AGH (pawilon D-16) przy ul. Kawiory 30.

Periodic table displays two types of metals with pronounced magnetic properties, namely d-metals with the d-states involved in metallic bonding, for which itinerant-electron description is appropriate, and lanthanides, in which the 4f states rest in atomic, i.e. non-bonding, states. Actinides with open 5f shell in a way interpolate between the two. The light actinides have the 5f states involved in bonding, the heavy ones (from Am onwards) have the localized 5f states. The crossover between the two regimes takes place at Pu. It is very instructive to investigate various Pu phases (by bulk techniques and spectroscopies) and deduce, that none of the two conventional approaches is capable to capture the reality, and one has to start to develop a new paradigm (as DMFT) which describes correctly the strongly-correlated nature of electron sub-system. Magnetic properties of actinides are also strongly affected by spin-orbit interaction due to their high atomic number Z. As Pu is close to the non- magnetic state 5f 6 , the magnetic features are much more pronounced at uranium. The orbital magnetism of bonding states has dramatically different mechanisms of exchange interaction, and related magnetic anisotropy energies reach enormous values. Moreover, the 5f magnetism is very sensitive to external variables. For example, hydrostatic pressure can induce non- monotonous variations of the Curie temperature, as demonstrated on the example of UGa 2 . Recently we have been dealing with ferromagnetic alloyed UH 3 , existing in several structure modifications, some of them having Curie temperature exceeding 200 K. Few example will be given to illustrate the peculiar character of the 5f magnetism.

Serdecznie zapraszamy na Środowiskowym Seminarium Fizyki Ciała Stałego, które odbędzie się w środę, 5 listopada o godz. 9:00 w sali 1.02A Akademickiego Centrum Materiałów i Nanotechnologii AGH (pawilon D-16) przy ul. Kawiory 30.

Układy trójwarstwowe Fe/MgO/Fe mają szerokie spektrum aplikacyjne ze względu na występujące w nich zjawisko tunelowego magnetooporu¹. Dla subnanometrowych grubości izolatora w układzie Fe/MgO/Fe tunelowanie prowadzi do antyferromagnetycznego sprzężenia warstw Fe, którego pochodzenie jest tłumaczone w pracach teoretycznych istnieniem wakancji tlenowych w warstwie MgO², czy relaksacją strukturalną złącza³. Nasze badania magnetycznych właściwości trójwarstw Fe/MgO/Fe potwierdziły istnienie antyferromagnetycznego (AFM) sprzężenia między warstwami Fe dla subnanometrowych grubości MgO. Co więcej, okazuje się, że zastosowanie homoepitaksjalnej buforowej warstwy MgO wpływa na wzmocnienie siły antyferromagnetycznego oddziaływania w układzie. Dla trójwarstw przygotowanych na buforze zaobserwowano dwukrotnie silniejsze sprzężenie między warstwami Fe niż dla układu przygotowanego bezpośrednio na podłożu MgO⁴.

1. S. Yuasa, T. Nagahama, A. Fukushima, Y. Suzuki, and K. Ando, Nature 3, 868 (2004).
2. M. Ye. Zhuravlev, E. Y. Tsymbal, and A. V. Vedyayev, Phys. Rev. Lett. 94, 026806 (2005).
3. H. X. Yang, M. Chshiev, A. Kalitsov, A. Schuhl, and W. H. Butler, Appl. Phys. Lett. 96, 262509 (2010).
4. A. Kozioł-Rachwał, T. Ślęzak, M. Ślęzak, K. Matlak, E. Młyńczak, N. Spiridis, and J. Korecki, J. Appl. Phys., 115 104301(2014).