Mechanomagnetics in Elastic Crystals: Insights from [Cu(acac)₂ ]

We predict that the magnetic properties of [Cu(acac)₂ ], an elastically flexible crystal, change drastically when the crystal is bent. It is found that unbent [Cu(acac)₂ ] is an almost perfect Tomonaga-Luttinger liquid. Broken-symmetry density-functional calculations reveal that the magnetic exchange interactions along the chains are an order of magnitude larger than the interchain exchange. The geometrically frustrated interchain interactions cannot magnetically order the material at any experimentally accessible temperature. The ordering temperature (T_N ), calculated from the chain-random-phase approximation, increases by 24 orders of magnitude when the material is bent. We demonstrate that geometric frustration both suppresses T_N and enhances the sensitivity of T_N to bending. In [Cu(acac)₂ ], T_N is extremely sensitive to bending but remains too low for practical applications, even when bent. Partially frustrated materials could achieve the balance of high T_N and good sensitivity to bending required for practical applications of mechanomagnetic elastic crystals.