Advanced functional materials: discovery of large coercive field in two dimensional spin glass

Since the separation of graphene in 2004 two-dimensional materials have been developed unprecedentedly show many strange properties in the fields of magnetism electricity force optics. Compared with other physical properties the research of two-dimensional magnet is relatively late. Although the possibility of two-dimensional magnet has been proved theoretically only a few materials have been verified experimentally. They include: cri3 MoS2 feps3 [crcl2 (pyrazine) 2] [Fe (bimcl) 3] cr2ge2te6 vse2 mnse2. The main reason is that the traditional magnetic materials are difficult to peel out two-dimensional layers. In the samples with a small number of layers two-dimensional magnets are easy to form three-dimensional magnetic long-range order through the magnetic interaction in chemical bonds or space thus masking the real two-dimensional behavior. Therefore blocking the magnetic interaction between two-dimensional material layers is the key to realize two-dimensional magnet. On the other h

two-dimensional materials with specific topological structure spin fault resistance characteristics generally show strange magnetic properties. Most of the studies based on kagome's theory are focused on the two-dimensional hexagonal lattice. Among them the ground state of honeycomb lattice is a semiclassical n é El ordered state with small quantum fluctuations which is very novel in theory. However it is difficult for real compounds to have ideal honeycomb lattices which often show varying degrees of distortion. One of the common distortions is that the two sides of the hexagon are significantly shortened to form a dimeric honeycomb lattice or square lattice with mixed spin. Interestingly the lattice exists in the famous magnetic insulator tlcucl3 the Bose Einstein condensation of Magnon is observed in the material. Therefore dimer honeycomb lattice can be used as a model system to study quantum phase transition. However up to now only a few dimeric honeycomb lattices with half integer spin centers have been reported none with integer spin centers have been reported.

Professor Zheng Yanzhen Institute of Frontier Science technology Xi'an Jiaotong University associate researcher Fu Zhendong Songshanhu material laboratory Dongguan have reported a two-dimensional van der Waals magnetic material [Fe (4-etpy) 2 (N3) 2] n (Fen) composed of dimeric honeycomb lattice with integer spin. The results of TEM SEM AFM show that the samples are stacked in layers the thinnest part is about 13 nm thick which is equivalent to ten layers of single-layer compound. Different from the common magnetic properties of long-range magnetic ordering Mossbauer spectroscopy polarized neutron scattering studies show that the material exhibits a reentrant spin glass behavior due to the exchange coupling interaction between ferromagnetism antiferromagnetism in the lattice has spin glass phases with different tilt angles at 39 K 28 K. Using cur é ly model two exchange coupling constants (J1 = 35.8cm − 1 J2 = − 3.7cm − 1) can be simulated. By analyzing the polarized neutron scattering data in the temperature range of 3.3 to 100k it is found that the magnetic interaction between the two-dimensional magnetic layers is effectively blocked. The further simulation of magnetic scattering also shows that the short-range spin correlation of the material has two-dimensional properties. The hysteresis loop measurement at 2 K shows that the material has a very large coercive field of 1.9 Tesla which proves that the material is a "very hard" two-dimensional van der Waals magnet. The researchers of

firmly believe that the combination of two-dimensional magnets topological spin frustration can produce some novel physical phenomena material properties which may open up a new direction for research. The follow-up work will start from reducing the thickness of the material designing a new ideal topology to further reveal the characteristics of this kind of two-dimensional magnetic materials. Relevant results are published online in advanced functional materials

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