Absence of a martensitic phase transformation (even an embryonic phase) in potassium as determined by an ultrasound study

The temperature dependence and magnetic-field dependence of the nonlocal generation of ultrasound were measured between 1.8 and 25 K in high-quality potassium single crystals. The wave associated with the elastic constant C', which is extremely sensitive to any structural phase transformation, was studied. These electromagnetic-generation experiments clearly show that no anomalies in the elastic behavior occur, either in the bulk or within the skin depth. These measurements lend no support to the existence of a martensitic phase transformation or to the existence of an embryonic martensitic state in stress-free bulk potassium single crystals or within the skin depth of these crystals.