**Acknowledgements**

*Solid State Physics - Metastable, Spintronics Materials and Mechanics of Deformable...*

Regarding the hemoproteins, they combine the presence of a porphyrin (iron protoporphyrin IX) as the redox center with the chiral protein structure that acts as a spin filter. To date, cytochrome *c* stands out as the hemoprotein for which the capacity to produce CISS effect has already been demonstrated experimentally. Porphyrins and hemoproteins also have proven potential for nanorobotic application. Porphyrins are particularly useful for nanorobotics applied to medicine because of their photochemical properties. Porphyrins also can self-assemble in structures such as J-aggregates to form nanotubes. On the other hand, the catalytic properties of hemoproteins are the most relevant factor that makes them applicable to self-propulsion in micro-/nanorobotics. The studies and applications of porphyrins and hemoproteins in spintronic and nanorobotic are still in their early stages, and a wide field of study of these compounds is open to the area of bioelectronics. Among the numerous advances that are possible for the field of spintronic, special attention has been given to spinterface, that is, the interface between a ferromagnetic (FM) metal and an organic semiconductor, in which unique hybrid states are formed. The FM metal/molecular interfaces constitute an important building block for the future of spintronics. The unique hybrid states of spinterfaces influence magnetic properties such as magnetic anisotropy, magnetic exchange coupling, interfacial spin polarization, and others. Further, the interactions between the FM metal and organic molecules are tunable in such a way that the spinterfaces are applicable to multifunctional devices meeting the industry tendency of miniaturization using single-molecule devices. The external control of spinterface by external signals, especially light because the ultra-fast optical transmission, is a promising area for future investigations. An important challenge for the design of spintronic devices is the changeable control and switch of single molecules adsorbed on the surface of FM materials. Particularly, for the metalloporphyrins, an interesting example is the use of axial ligands of the porphyrin transition metal center to change the magnetism of the molecular

was able to reversibly switch the spin state of the Co and

Fe of porphyrins adsorbed on Ni(001) Co substrates, respectively. Similarly, NH3 was able to induce the transition of Ni porphyrin on Co substrate from low to high spin states [99, 100]. Another emerging field of spintronics is the use of antiferromagnets that are affected by spin-polarized currents. Antiferromagnetic materials have several advantages for spintronics such as they do not create external magnetic fields and only weak interactions occur with each other and the antiferromagnets have the characteristic frequencies of switching between their states significantly higher than the values obtained for ferromagnets. Further, the occurrence of ordering in antiferromagnets it is more frequent and occurs at soft conditions than in ferromagnets. Also, these materials can behave as a conductor for a spin polarization and as an insulator for other spin polarization. The antiferromagnets can provide desirable characteristics for spintronics that are high speed of operation in terahertz range, performance, easy manipulation, high

The field of micro/nanorobotics that also can take advantage of the properties of porphyrins and hemeproteins has as the principal challenge for advances as the control and powering of the movement. The crescent interest in the application of MNR in theranostic poses the additional challenge for the use of biocompatible and high-performance materials and fuels. An interesting alternative regarding the elimination of toxic fuels is the use of systems having the propulsion powered by external field that are fuel-free and allow the remote control of the movement. The MNRs with a real potential to operate in vivo are rare now and constitute an important area for future investigations that requires multi- and interdisciplinary

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studies [102].

component [98]. NO•

sensitivity, and low energy cost [101].

The author thanks FAPESP 2015/017688-0, 2017/02317-2, SisNano (402289/2013-7), NBB/UFABC, CAPES grant 001, and CNPq (309247/2017-9) for the financial support and CEM/UFABC for the access to facilities.
