Elucidation of the fundamental science by establishing structure-function relationships to identify new magnets with technologically important properties and exploiting the anomalous magnetic properties we already discovered for ruthenium-based magnets is goal of this project. The targeted properties include: including enhanced ordering temperatures (Tc), controllable coercive fields (Hcr), and to extend and exploit their anomalous magnetic properties. The [Ru2(O2CMe)4]3[Cr(CN)6] magnet (Tc = 33 K) has 2 interpenetrating lattices that lead to anomalous hysteresis and zero-field cooled/field cooled magnetization etc. Its Tc reversibly increases by 79% to 59 K with applied pressure, and the anomalous wasp-waist shaped hysteresis becomes normal at 12.8 kbar. Identifying the genesis and extending and exploiting the magnetic consequences of the interpenetrating lattice for this family of magnets are targeted. The 2nd lattice leads to anomalous behaviors, and it is a rare example of new phenomena arising from a 2nd lattice. New examples with higher Tc and coercivity controllable by pressure will be identified. Magnets composed of [FeII/III2(O2CR)4]+ (S = 9/2), [Ru2(O2CR)4]n (n = 0, 2+), [Ru(CN)6]3-, [Os2(O2CR)4]+, and [M(NCS)6]3- composition are sought. Also, control of the sign of spin coupling (J) to observe ferromagnetic not ferrimagnetic coupling will be validated by making and studying [M2(O2CMe)4]3[Cr(CN)6] (M = Rh, Mo). This work is supported by the Solid State and Materials Chemistry program in the Division of Materials Research at the NSF.
NON-TECHNICAL SUMMARY:
Magnetism is scientifically and technologically exceedingly important as it is the basis of a $20-billion/yr industry. Organic-based magnets enable the development of new families of magnets with combinations of properties not previously observed as well as providing a deeper and broader understanding of magnetism to form a stronger foundation for next-generation materials and devices. Control of magnetic behavior via structure control, especially for interpenetrating structures, will lead to the development of new and enhanced properties for future hybrid multifunctional materials. Developing and exploiting new materials is key to next generation devices, and is essential for the training of undergraduate students, graduate students, and post-doctoral scholars in many interdisciplinary aspects of materials chemistry with emphasis on the design, synthesis, chemical, and magnetic characterization of a new class of magnets. This research endeavor lends itself to outreach activities such as talks with audience participation to K-12 students and community audiences, as well as having minority high school and undergraduate students participate in research activities and assist journalists with their reports on technical topics. The study of new magnetic materials is a worldwide enterprise, and existing worldwide collaborations with scientists in the UK, Spain, Russia, Korea, Japan, and Greece will be strengthened and expanded. This work is supported by the Solid State and Materials Chemistry program in the Division of Materials Research at the NSF.
Magnets are technologically and scientifically exceptionally important and these magnets are based on metals or their oxides with atomic building blocks. Using entire molecules as building blocks has enabled the development of new families of magnets exhibiting unusual magnetic properties in combination with other technologically important properties that classical, commercial magnets do not exhibit. This work provides the foundation to understand magnetism to a greater extent, and develop new magnetic materials with enhanced properties and to exploit applications. By controlling the structure and composition the magnetic behavior can be modulated. In this regard, we have identified that the magnetic structure and properties of a magnet uniquely possessing two identical, but interpenetrating three dimensional (3-D) lattices whose magnetic property changes with pressure suggesting its use as a pressure senor/switch. The mechanism and properties as a function of pressure, temperature, and applied magnetic field has been worked out. While it was anticipated that the iron analog would exhibit similar properties, another behavior was observed. The pressure dependence of a different family member with a layered (2-D) structure had a different behavior with a 32% increase in ordering temperature with applied pressure. In addition to the 3-D and 2-D layered structured materials, an example of a 1-D chain structure material was made. The results of this research has been published in peer reviewed journals and parts have been presented at conferences. As molecule-based materials are increasingly essential for future materials/systems, and training and integration in this area is crucial, and this research importantly provides the needed interdisciplinary training of undergraduate/graduate students/post-doctoral scholars in the design, synthesis, chemical, and magnetic characterization of a new class of magnets as being representative of molecule-based materials in general. While magnetism is thought to be mature, studies of molecule-based magnets have led to a broader understanding of magnetism in the physics and materials science communities, and we have established collaborations with scientists worldwide as well as hosted students/PIs from other groups that broaden our co-workers training. Also, identification of new phenomena arising from interpenetrating lattices should impact other scientific areas, and the new properties should lead to important new classes of materials. Forming/thwarting interpenetrating lattices should enable complex materials with controlled properties, e.g. hybrid, multifunctional materials (meta-material), e.g. piezomagnetic/magnetic switches. Furthermore, due to the still-growing technological importance of magnets, new materials with enhanced and combinations of properties will impact applied physics/materials science research.
