Magnetic-Field-Induced Strong Negative Thermal Expansion in La(Fe,Al)13

Negative thermal expansion (NTE) plays an increasingly important role in the control of thermal expansion of materials. However, the discovery of strong NTE materials, which is rare, remains challenging. In this study, a strong NTE (alpha(1) = -14.01 x 10(-6 )K(-1)) has been achieved in La(Fe11.5Al1.5) by a new method of loading magnetic field, which is different from the conventional method of chemical modification. The strong NTE of La(Fe11.5Al1.5) originates from the enhanced ferromagnetic (FM) component induced by the magnetic field-driven spin-moment rotation of the canting structure, which has been revealed by the magnetic field and temperature dependence of neutron powder diffraction and small-angle neutron scattering. Furthermore, the hidden short-range FM order facilitates a wider NTE temperature range in La(Fe11.5Al1.5). This study provides the possibility that an external environment, such as a magnetic field, can be an effective approach to control or achieve strong NTE in functional materials.