First order magneto-structural transition in functional magnetic materials: phase-coexistence and metastability

Abstract

First order magneto-structural transition plays an important role in the functionality of various magnetic materials of current interest like manganese oxide systems showing colossal magnetoresistance, Gd 5 (Ge, Si) 4 alloys showing giant magnetocaloric effects and magnetic shape memory alloys. The key features of this magneto-structural transition are phase-coexistence and metastability. This generality is highlighted with experimental results obtained in a particular class of materials. A generalized framework of disorder influenced first order phase transition is introduced to understand the interesting experimental results which have some bearing on the functionality of the concerned materials.

Opposite Thermal Expansion in Isostructural Noncollinear Antiferromagnetic Compounds of Mn3A (A = Ge and Sn)

“…Note that most available NTE alloys are ferromagnetic (FM), whereas the present Mn 3 Ge exhibits an antiferromagnetic structure. Furthermore, even a high Neel temperature ( T N ) is found in the present Mn 3 Ge ( T N = 380 K) when compared with other antiferromagnetic intermetallic compounds, such as YMn 2 ( T N = 100 K), Gd 5 Ge 4 ( T N = 125 K), and CeFe 2 ( T N ∼ 90 K) . Because of the magnetostriction effect, the dimensions of FM alloys can be influenced by the external magnetic field.…”

“…Furthermore, even a high Neel temperature (T N ) is found in the present Mn 3 Ge (T N = 380 K) when compared with other antiferromagnetic intermetallic compounds, such as YMn 2 (T N = 100 K), 39 Gd 5 Ge 4 (T N = 125 K), 40 and CeFe 2 (T N ∼ 90 K). 41 Because of the magnetostriction effect, the dimensions of FM alloys can be influenced by the external magnetic field. However, AFM compounds can avoid the negative effect of the external magnetic field on the precise dimension.…”

Peculiarities of the phase transformation dynamics in bulk FeRh based alloys from magnetic and structural measurements

“…Phase coexistence is a rather general and curious phenomenon for many materials experiencing first-order magnetic phase transitions (FOMT) [1][2][3]. At the same time, explanations of this phenomenon within the mechanisms of interaction of electrons or imperfections of chemical composition and structure still seem inconclusive [4,5].…”

Enhancing ferromagnetism in the kinetically arrested LaFe12B6 by partial La/Nd substitution

“…Second-order AFM-FM metamagnetic transitions are observed frequently, while their first-order counterparts are rather rare. The latter have been reported, for example, in doped CeFe2, [1][2][3][4][5] Ge-rich Gd5Ge4-xSix, [6][7][8][9][10] Nd5Ge3, [11] Hf1xTaxFe2, [12] FeRh, [13] Mn1xCrxCoGe, [14] DySb, [15] ErRu2Si2, [16] HoCuSi, [17] and a few other intermetallic compounds, Many of these first-order transitions reveal complex and interesting features in their isothermal magnetization, such as avalanches or steps that may occur sequentially in staircase-like patterns.…”