Beating the Size-Dependent Limit with Spin-Lattice Coupling in Nanomagnetism

Further miniaturization of magnetic nanomaterials is intrinsically accompanied by a reduction in spin ordered domains, resulting in size-dependent magnetic behaviors. Consequently, a longstanding roadblock in the advancement of nanodevices based on magnetic nanomaterials is the absence of a method to beat the size-dependent limit in nanomagnetism. Here, we discover and exploit a spin-lattice coupling effect in three-dimensional freestanding magnetic nanoparticles to beat the size-dependent limit for the first time. The so-called spin-lattice coupling involves varying spin configuration and exchange constant of spin interactions induced by lattice deformations. We correlate spin-lattice coupling to g-shift and employ two-dimensional magnetic resonance imaging to visualize g-factor. As lattice constants decrease (even similar to 1%), positive offset of g-shift increases significantly, signaling stronger spin-lattice coupling, which induces a transition from paramagnetism to surperparamagnetism, thereby effectively beating the size-dependent limit.