NANOPARTICLES OF EXOTIC EPSILON-IRON OXIDE (III) AS THE WORKING ENVIRONMENT OF NANOMAGNETIC LOGIC DEVICES

 Subject of Research.The paper discusses the principles of information processing by nanomagnetic logic devices consisting in the magnetization manipulation of individual magnetic nanoparticles in a single-domain state and combined into a logical network. In a single-domain state, nanoparticles have uniaxial magnetic anisotropy that makes them a bistable system suitable for binary coding of information: the magnetization downwards corresponds to a logical "0", the magnetization upwards is "1". These two states are separated by an energy barrier with the height equal to the energy of the magnetic anisotropy. The logical network in question implies an entirely new way for performing of logical operations. The point at issue is about a network of nanomagnets connected by a dipole interaction and admitting the existence of intermediate frustrated states, analogous to quantum entanglement. Methods. Materials with sufficiently high magnetic anisotropy energy are required for nanomagnetic logic devices to ensure that thermal fluctuations do not lead to orientation loss of magnetic moment and the loss of information. As such, we proposed to use new nanomagnets based on the epsilon phase of iron oxide ε-Fe₂O3 with giant magnetic anisotropy. Nanoparticles are produced by a combination of two methods: synthesis in reverse micelles and a sol-gel method. Elemental analysis of nanoparticles was carried out by mass spectrometry with inductively coupled plasma (Agilent Technologies, HP 4500). Photomicrographs were obtained by the JEOL JEM 2000EXII transmission microscope. The structure of nanoparticles is determined by X-ray diffraction on a Rigaku RINT2100 instrument. Study of the magnetic properties was carried out with the use of SQUID magnetometer Quantum Design, MPMS 5XL. Main Results. A new method for performing of logical operations is proposed that consists in the magnetization manipulation of individual nanoparticles not only with the aid of an external magnetic field, but also by varying the temperature of the ε-Fe₂O₃ nanoparticles under the conditions of a spin-reorientation transition. In the ε-Fe₂O₃ nanoparticles, a magnetoelectric interaction is discovered that opens new ways for solving the bit state reading problem in the devices under consideration. Experimental conditions for performing of logical operations in ordered arrays of ε-Fe₂O₃ nanoparticles are created. Practical Relevance. Temperature manipulation by the vector magnetization direction opens up new possibilities for creating devices for nano-magnetic logic and spintronics under conditions of strong anisotropy, when the magnetic fields required to switch the direction of magnetization (and, hence, the change in the bit state) become unacceptably large. The principles discussed in the paper are capable of providing a nondissipative processing of information in the energy limit close to Landauer's estimates, where thermodynamic aspects come to the fore.