X-Ray and Susceptibility Study of the First-Order Magnetic Transformation in Mn3Pt

Abstract

The first-order transformation from triangular to collinear antiferromagnetic structure (AF-AF transformation) has been investigated in the Mn3Pt1−xRhx and Mn3+yPt1−y systems by x-ray diffraction and magnetic methods. At the AF-AF transformation temperature Tt a discontinuous change in the lattice parameter is observed with a magnitude depending on concentration but with always the same lattice parameter value of the collinear phase. This implies the existence of a critical lattice parameter value for the AF-AF transformation. Below the Néel temperature TN an anomaly in the thermal expansion occurs indicating exchange interactions dependent on the interatomic separation. This anomaly differs in sign for the collinear-paramagnetic and triangular-paramagnetic transitions. The susceptibility shows an abrupt change at Tt and a maximum at TN in the triangular phase. No maximum occurs for the collinear phase. The observed transition temperatures are in agreement with the earlier neutron diffraction data.

Ab initiotheory of the Gibbs free energy and a hierarchy of local moment correlation functions in itinerant electron systems: The magnetism of theMn3Amaterials class

“…Below this value the collinear AFM state is entirely suppressed and a single second-order triangular AFM-PM transition occurs. T N ≈ 800K for a > a c , somewhat higher than the experimental value of 475K [5][6][7] . Notably, our DFT-DLM approach correctly predicts the two triangular and collinear AFM orderings as the most stable phases and explains the occurrence of the first-order transition as a magnetovolume driven effect.…”

“…2(a)) 88,89 , Mn 3 Pt shows a second-order collinear AFM-PM transition when cooling through T N = 475K (Fig. 2(b)) [5][6][7]88 . The corresponding magnetic unit cell of the collinear AFM phase is twice (and so tetragonal) the crystallographic unit cell.…”

“…For example, non-collinear AFM triangular states arise from the formation of Kagome-type lattice planes in both the cubic and hexagonal lattices 20 , whilst the tetragonal systems show collinear FIM 8,19,87 . The material that perhaps exhibits the most intriguing frustrated magnetism is cubic Mn 3 Pt, in which the high temperature collinear AFM phase has been observed experimentally to have an apparent zero net magnetization at some Mn sites [5][6][7] . It is a challenging test of our DLM theory to provide an explanation for this apparent oddity as well as the disparate magnetic properties of the other Mn 3 A systems.…”

“…The Mn 3 A (A=Pt, Ir, Rh, Sn, Ga, Ge) class of magnetic materials in all its crystal structures (cubic, hexagonal, and tetragonal) is chosen as a striking case study. These systems are challenging tests for our theory owing to their large variety of phase transitions and magnetic phases, such as collinear and non-collinear antiferromagnetic states [3][4][5][6][7] and ferrimagnetism 8,9 . The class has high relevance for spintronics [10][11][12][13][14][15][16][17] and for the fundamental understanding of frustration 18,19 and spin chirality 20 .…”

Contribution of community-based sociotherapy interventions for the psychological well-being of Rwandan youths born to genocide perpetrators and survivors: analysis of the stories telling of a sociotherapy approach

“…The study design used was an exploratory qualitative method based on a case study approach, represented by participant responses given in the sociotherapy sessions and conviviality meetings. Qualitative research is a systematic scientific inquiry which seeks to build a holistic, largely narrative, description to inform the researcher's understanding of a social or cultural phenomenon [44]. The case study was used for describing an entity that forms psychosocial well-being among youths assigned to the community-based sociotherapy intervention in the southern province of Rwanda.…”