Magnetic and magnetocaloric properties of Gd6(Mn1−xCox)23 compounds (x ≤ 0.3)

The magnetic and magnetocaloric properties of the Th6Mn23-type structure Gd6(Mn1−xCox)23 (x ≤ 0.3) compounds are investigated from DC magnetization measurements. The Curie temperature of these ferrimagnetic materials evolves non-continuously with the Co content from TC = 489 K for x = 0 to TC = 118 K for x = 0.3. In relation with the lower magnetic moment of Co atoms compared with that of Mn atoms, the Co to Mn substitution leads to a decrease of the maximal magnetization, recorded at 5 K in an applied magnetic field of 9 T, from 54.7 μB/f.u. for x = 0 to 36.3 μB/f.u. for x = 0.3. These materials present an anomalous magnetocaloric effect, characterized by two broad -ΔSM maxima of moderate magnitude at TC and around 100 K, yielding to wide magnetocaloric response from TC down to the lowest temperature, and consequently, a relatively large cooling capacity q10-350K (μ0ΔH = 5 T) reaching ∼ 3.7 J cm−3 for Gd6(Mn0.875Co0.125)23. The results are analyzed and discussed in connection with previously published data.