Tailoring the magneto-structural coupling in Mn1−xZrxCoGe alloys

In the present work, we have demonstrated that the coupling and decoupling between the magnetic and structural transitions can be manipulated by the partial replacement of the Mn by Zr in the MnCoGe alloys. Energy-dispersive spectroscopy analyses reveal a homogeneous distribution of the Zr atoms throughout the samples. The differential scanning calorimetry and X-ray diffraction results reveal a decrease in the structural transition temperature Tt with an increase in the Zr content. A strong magneto-structural coupling can be realized in the Mn1−xZrx CoGe with 0.04 ≤ x ≤ 0.07, where the Tt is lowered to the temperature range between the Curie temperatures of the orthorhombic and hexagonal phases. The magneto-structural transition is accompanied with significant changes in the interatomic distances between the magnetic atoms, which strongly influence both the magnetic exchange interactions and the chemical bonding. As a result, a coincidence of the magnetic and structural transitions is observed, which brings a giant magnetocaloric effect due to the contributions from both the lattice and the magnetic entropy changes.