Thermomagnetic study of the antiferromagnetic solid solutions pMnO-qCoO (p+q=1)

Abstract

Precise measurements have been made of the specific heats of the antiferromagnetic solid solutions pMnO-qCoO and of the pure oxides MnO and CoO in the temperature range 20 to 700K. From these measurements, the Neel temperatures have been deduced and, through the application of the BPW effective field model, the exchange integrals have been estimated: in spite of the change which occurs in the lattice parameter, these integrals appear to remain effectively constant over the range of compositions. A hybrid method based on a combination of the corresponding states method with the effective phonon spectrum has been found to give consistent results when the lattice contribution is separated for MnO and CoO. There is good agreement between the experimental and theoretical entropy for most of the range of compositions. However, there appears to be some anomalous behaviour for the magnetic energy where there is small substitution of one oxide in the other.

Assessment of the Mn-O system

“…74 combusion Mixter [94] 525.02 combusion Siemonsen [98] 525.02 combusion Ulich and Siemonsen [99] 521. 84 solution Shomate [47] 521. 26 assessed Rossini [103] 520 assessed Brewer [102] 520.…”

“…26 assessed Rossini [103] 520 assessed Brewer [102] 520. 84 assessed Mah, [101] Zordan and Hepler [108] 520. 38 assessed Pankratz [107] 522.0 assessed Knacke et al [106] 520.…”

“…A number of measurements of the heat capacities of the oxides Mn 1−x O, [46,[84][85][86] Mn 3 O 4 , [46,60,87] Mn 2 O 3 , [60,88] and MnO 2 [46,60,89] have been performed. These measurements are compared to the curves optimized in this work in Fig.…”

Formation and magnetic behaviour of manganese oxide nanoparticles

“…On the other hand, inset of Fig. 7 depicts one peak with T N = 120 K for pure MnO formed by decomposition of oxalate at 500 • C and 600 • C for 5 h each in nitrogen ambient; the known T N being in the range 118-122 K [40][41][42]. But, the peak in is known to occur at a temperature slightly higher (by few %) than T N [43][44][45].…”

Thermodynamic modeling of the CeO2–CoO phase diagram

“…The heat capacity data of the solid and liquid phases, however, are available for only a few oxides and are sometimes inaccurate [14]. There exist some heat capacity data of only solid phase for CeO 2 [15] and for CoO [15][16][17][18]. Therefore, in the present work, the difference in the heat capacities of the liquid and solid phases were neglected to calculate the interaction parameters of the solid and liquid solution phases.…”