Anomalous thermal expansion and magnetic critical behavior in ErFe12− x Ti x

Rare-earth-transition-metal compounds with a ThMn12-type structure exhibit high Curie temperature (TC), large saturation magnetization, and tunable magnetic anisotropy, making them promising for permanent magnets and multifunctional magnetoelastic materials. In this work, we systematically investigated the zero thermal expansion (ZTE) behavior, magnetoelastic coupling mechanism, and magnetic critical behavior of ErFe12−xTix (x = 1.0, 1.1) using temperature-dependent neutron powder diffraction, magnetic measurements, and thermal dilatometry. The results demonstrate that ErFe10.9Ti1.1 exhibits excellent ZTE properties over 447–507 K. Rietveld refinement indicates that the ZTE originates from the pronounced spontaneous volume magnetostriction (ωs) induced by strong magnetoelastic coupling near TC. Critical behavior analysis reveals that the system undergoes a second-order magnetic transition dominated by long-range exchange interactions. Due to the weakening of long-range magnetic order and residual non-phononic volume contributions, a distinct deviation exists between the macroscopic characteristic temperature (TZTEend ≈ 507 K) and the microscopic lattice characteristic temperature (T* ≈ 525 K) of the system.