Investigation of the critical behavior in Mn0.94Nb0.06CoGe alloy by using the field dependence of magnetic entropy change

Abstract

Dou, S. X. (2013). Investigation of the critical behavior in Mn0.94Nb 0.06CoGe alloy by using the field dependence of magnetic entropy change. Journal of Applied Physics, 113 (9), 093902-1-093902-5.Investigation of the critical behavior in Mn0.94Nb 0.06CoGe alloy by using the field dependence of magnetic entropy change AbstractThe critical behaviour of Mn0.94Nb0.06CoGe alloy around the paramagnetic-ferromagnetic phase transition was studied based on the field dependence on magnetic entropy change. By using the obtained exponents, the modified Arrott plot is consistent with that by using conventional method. These critical exponents are confirmed by the Widom scaling relation. Based on these critical exponents, the magnetization, field and temperature data around Tc collapse into two curves obeying the single scaling equation MðH; e)¼ebf6(H/ ebþc). The calculated critical exponents not only obey the scaling theory but also anastomose the deduced results from the Kouvel-Fisher method [ J. S. Kouvel and M. E. Fisher, Phys. Rev. 136, A1626 (1964)]. The values deduced for the critical exponents in the Mn0.94Nb0.06CoGe alloy are close to the theoretical prediction of the mean-field model, indicating that the magnetic interactions are long range. This method eliminates the drawback due to utilization of multistep nonlinear fitting in a conventional manner. So it provides an alternative method to investigate the critical behaviour. The critical behaviour of Mn 0.94 Nb 0.06 CoGe alloy around the paramagnetic-ferromagnetic phase transition was studied based on the field dependence on magnetic entropy change. By using the obtained exponents, the modified Arrott plot is consistent with that by using conventional method. These critical exponents are confirmed by the Widom scaling relation. Based on these critical exponents, the magnetization, field and temperature data around Tc collapse into two curves obeying the single scaling equation

Ti substitution for Mn in MnCoGe – The magnetism of Mn0.9Ti0.1CoGe

“…In this way a single first-order magnetostructural transition leading to an enhanced magnetocaloric effect near room temperature can be derived [12,13,18]. Recently, in order to realize the desired magnetostructural coupling, lots of efforts have been made in different ways to modify the MnCoGe/MnNGe compostions [12][13][18][19][20][21][22][23][24] .…”

Magnetocaloric effect and magnetostructural coupling in Mn0.92Fe0.08CoGe compound

“…Importantly, the value of T str depends strongly on several factors including: external pressure, 8 the vacancies in the Co and Mn sites, as well as variation in chemical environment due to element substitution on Mn, Co, or Ge sites. [9][10][11][12][13][14][15][16][17] Recently, MnCoGebased compounds have attracted significant attention; [9][10][11][12][13][14][15][16][17] this is due mainly to the strong coupling between magnetism and structure in these materials. This coupling in turn can lead to MnCoGe-based materials, which exhibit large entropy changes and associated magnetocaloric effects, thereby offering scope for magnetic refrigeration around room temperature.…”

“…In order to achieve coincidence of magnetic and structural transitions which differ by around 300 K in the parent MnCoGe compound, several approaches to modify the Mn environments have been adopted. [9][10][11][12][13][14][15][16][17] Several studies concerning substitution of other elements for Mn, Co, or Ge have been reported in order to shift and thereby control the transition temperatures T str and T C . [9][10][11][12][13][14] The general aim of such studies is to cause the magnetic and structural transitions to coincide or overlap closely and thereby capitalise on both the magnetic and structural entropies at the resultant magnetostructural transition.…”

“…[9][10][11][12][13][14][15][16][17] Several studies concerning substitution of other elements for Mn, Co, or Ge have been reported in order to shift and thereby control the transition temperatures T str and T C . [9][10][11][12][13][14] The general aim of such studies is to cause the magnetic and structural transitions to coincide or overlap closely and thereby capitalise on both the magnetic and structural entropies at the resultant magnetostructural transition. [10][11][12][13][14] In this work, we report the structural and magnetic properties of Mn 0.92 Fe 0.08 CoGe compound as determined by high resolution, high intensity synchrotron x-ray diffraction studies and detailed magnetic measurements.…”

Influence of the demagnetizing factor on the magnetocaloric effect: Critical scaling and numerical simulations

“…[20][21][22][23][24][25] However, materials with first-order phase transitions do not collapse onto a universal curve and this fact can be used to determine the nature of the phase transition in a given material. 26 For h > 0, we expect a collapse for both first and second-order phase transition materials due to the paramagnetic behavior.…”