Controlling the Temperature of the Spin-Reorientation Transition In HoFe1-xMnxO3 Orthoferrite Single Crystals

TL;DR

This study investigates how manganese substitution in HoFe1-xMnxO3 crystals influences the spin-reorientation transition temperature, magnetic transition order, and structural phase, revealing a significant shift towards room temperature with increased Mn content.

Contribution

It demonstrates the control of the spin-reorientation transition temperature through manganese doping in HoFeO3, including structural, magnetic, and exchange interaction changes.

Findings

Transition temperature increases from 60 K to room temperature with Mn doping.

Magnetic transition changes from second-order to first-order.

Structural transition from orthorhombic to hexagonal at high Mn concentrations.

Abstract

HoFe1-xMnxO3 (0 < x < 1) single crystals have been grown by the optical floating zone technique. A structural transition from the orthorhombic to hexagonal modification has been established in the crystals in the concentration range of 0.7-0.8, which has been confirmed by the X-ray diffraction data. For a series of the rhombic crystals, the room-temperature Mossbauer study and magnetic measurements in the temperature range of 4.2-1000 K have been carried out. It has been observed that, with an increase in the manganese content in the samples, the temperature of the spin-reorientation transition increases significantly: from 60 K in the HoFeO3 compound to room temperature in HoFe0.6Mn0.4O3. The magnetic measurements have shown that, upon substitution of manganese for iron, the magnetic orientational type transition changes from a second-order transition (AxFyGz -> CxGyFz) to first-order one (AxFyGz -> GxCyAz) with a weak ferromagnetic moment only in the b direction (for Pnma notation). The growth of the spin-reorientation transition temperature has been attributed to the change in the value of the indirect exchange in the iron subsystem under the action of manganese, which has been found when studying the Mossbauer effect in the HoFe1-xMnxO3 (x < 0.4) compound.