Neutron powder diffraction investigation of magnetic structure and spin reorientation transition of HoFe1-xCrxO3 solid solutions

• With Cr-substitution in the HoFe1−xCrxO3 system, A Γ42 spin reorientation of Fe(Cr)3+ was observed with an increase in transition temperature from 56 K to about 200 K for x=0−0.6.
• The saturated moment of Fe(Cr) position was found to be systematically less than the ideal value of free ion, and thus implies the presence of spin quantum fluctuation.
• A composition–temperature phase diagram throughout x=0–1 for HoFe1−xCrxO3 system was established.

Orthoferrite solid solution HoFe1−xCrxO3 (x=0, 0.2,…,1.0) was synthesized via solid state reaction methods. The crystal structure, magnetism and spin reorientation properties of this system were investigated by X-ray diffraction, neutron powder diffraction and magnetic measurements. For compositions of x≤0.6, the system exhibits similar magnetic properties to HoFeO3. With increasing Cr-doping, the system adopts a Γ4(GxAyFz) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ42 spin reorientation of Fe(Cr)3+ was also observed in this system with an increase in transition temperature from 56 K to about 200 K due to competition between the Fe(Cr)–Fe(Cr) and Ho–Fe(Cr) interactions. For the x≥0.8, the system behaves more like HoCrO3 which adopts a Γ2(FxCyGz) configuration with no spin reorientation below the Neel temperature TN. Throughout the whole substitution range, we found that the saturated moment of Fe(Cr) was less than the ideal value for a free ion, which implies the existence of spin fluctuation in this system. A systematic magnetic structure variation with Cr-substitution is revealed by Rietveld refinement. A phase diagram combining the results of the magnetic measurements and neutron powder diffraction results was obtained.