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The structural properties of Mn0.92Fe0.08CoGe have been investigated in detail using synchrotron x-ray diffraction in zero and applied pressure (p=0-10 GPa). A ferromagnetic transition occurs around TC=300K and a large magnetic-entropy change -ΔSM=17.3 J/kg K detected at TC for a field change of ΔB-5 T. The field dependence of -ΔSMmax can be expressed as -ΔSMmax β B. At ambient temperature and pressure, Mn0.92Fe0.08CoGe exhibits a co-existence of the orthorhombic TiNiSi-type structure (space group Pnma) and hexagonal Ni2In-type structure (space group P63/ mmc). Application of external pressure drives a structure change from the orthorhombic TiNiSitype structure to the hexagonal Ni2In-type structure. A large anomaly in heat capacity around TC is detected and the Debye temperature θD (=319(±10) K) has been derived from analyses of the low temperature heat capacity, T ≲ 10 K. [ABSTRACT FROM AUTHOR]

Layered rare earth compounds in the RMn2X2 series (R = rare-earth; X = Ge, Si) are of interest for potential cooling applications at lower temperatures as they enable the structural and magnetic behavior to be controlled via substitution of R, Mn, and X atoms on the 2a, 4d, and 4e sites respectively. We continue investigations of the Pr1− xY xMn2Ge2 magnetic phase diagram as functions of both composition and Mn-Mn spacing using X-ray and neutron diffraction, magnetization and differential scanning calorimetry measurements. Pr1− xY xMn2Ge2 exhibits an extended region of re-entrant ferromagnetism around x ∼ 0.5 with re-entrant ferromagnetism at [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of seven CeMn2Ge2-xSix compounds with x = 0.0-2.0 have been investigated in detail. Substitution of Ge with Si leads to a monotonic decrease of both a and c along with concomitant contraction of the unit cell volume and significant modifications of the magnetic states - a crossover from ferromagnetism at room temperature for Ge-rich compounds to antiferromagnetism for Si-rich compounds. The magnetic phase diagram has been constructed over the full range of CeMn2Ge2-xSix compositions and co-existence of ferromagnetism and antiferromagnetism has been observed in CeMn2Ge1.2Si0.8, CeMn2Ge1.0Si1.0 and CeMn2Ge0.8Si1.2 with novel insight provided by high resolution neutron and X-ray synchrotron radiation studies. CeMn2Ge2-xSix compounds (x = 0, 0.4 and 0.8) exhibit moderate isothermal magnetic entropy accompanied with a second-order phase transition around room temperature. Analysis of critical behaviour in the vicinity of TCinter for CeMn2Ge2 compound indicates behaviour consistent with three-dimensional Heisenberg model predictions. [ABSTRACT FROM AUTHOR]