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Exchange Bias in Bulk Heusler Systems
Published in S. K. Sharma, Exchange Bias, 2017
In this chapter, we present a consolidated picture on the investigations reported on exchange bias (EB) phenomenon in bulk and ribbon forms of various ferromagnetic (FM) shape memory alloys belonging to the full Heusler family, mainly from the Ni–Mn-based subclass. In the last decade, full Heusler alloys have become one of the most important classes of materials because of their interesting magnetic and other multifunctional properties such as shape memory effect [1], magnetocaloric effect [2], magnetic superelasticity [3], giant magnetoresistance (MR) [4], and EB [5]. Most of these properties are associated with their first-order structural (i.e., martensitic) transition [6]. Magnetic, magnetocaloric, and electrical transport properties of these alloys have been extensively studied by many researchers, which have resulted in a large number of papers. Among these alloys, Mn-based alloys have been found to be singularly important. EB effect is one of the most important properties exhibited by a large number of full Heusler alloys. Though it is quite difficult to take into account all the wealth of information, we have tried our best to present a comprehensive picture regarding the EB aspects of these alloys in the bulk and ribbon forms.
Robustness in half-metallicity, thermophysical and structural properties of Co2YAl (Y = Pd, Ag) Heuslers: a first-principles perspective
Published in Molecular Physics, 2022
Ashwani Kumar, Saurabh Singh, Shakeel Ahmad Sofi, Tarun Chandel, Naveen Thakur
Recently, Heusler alloys have emerged as extraordinary multifunctional candidates especially in the field of spintronics. They instigated a great motivation to devise ultramodern devices from their discovery in 1903 by Friedrich Heusler [5]. Due to outstanding and exceptional properties Heuslers attract adequate attention [6–8]. They are ternary intermetallic compounds in the stoichiometry X2YZ, where X and Y are transition metal atoms and Y are from the main group sp elements. Heusler alloys can be classified into two main groups, the ternary and quaternary, the ternary group further consists of half [XYZ], full [X2YZ] and quaternary [XX’YZ]. The ternary group full Heuslers (X2YZ) type owns two types of structures, Cu2MnAl structure with space group #225, Fm-3 m and the other is Hg2CuTi structure with space group #216, F43m. The Wycoff positions occupied in prototype Cu2MnAl system are A (0, 0, 0) and B (1/2, 1/2, 1/2), Y and Z atoms occupy the C (1/2, 1/2, 1/2) and D (3/4, 3/4, 3/4) positions, respectively. If the number of valence electrons of Y elements exceeds those of X elements, then the Hg2CuTi-type crystal structure will form, while if X element’s valence electrons found more than that of the Y one, Cu2MnAl type will form [9–13].
An ab initio study on the structural, electronic and mechanical properties of quaternary full-Heusler alloys FeMnCrSn and FeMnCrSb
Published in Philosophical Magazine, 2018
Heusler alloys are multifunctional materials which have remarkable properties for spintronic and magnetoelectronic applications with specific electronic band structure, structural and magnetic character. In this view, there are several studies about Heusler alloys in literature. Gillessen and Dronskowski studied some physical properties of Heusler alloys within first-principles calculations [10,11]. Some researchers have focused on these alloys since they have high Curie temperature (Tc) and large magnetisation [12,13] and complete spin polarisation at Fermi level (EF) which is important parameter for spin-dependent devices [14]. It is found that Heusler-type Co2FeAl and Co2FeAl0.5Si0.5 materials show great tunneling magnetoresistance ratios [15–17]. Although it is well known that many Heusler alloys are half-metallic ferromagnets [2,18–22], some of them have disordered structure which can destroy half-metallicity and affect magnetoresistance ratio [23–25]. Furthermore, there are many studies about this type of alloys in literature [26–30].
Half-metallic ferromagnetism in new quaternary Heusler alloys CoX’YP (X’ = Cr and Fe)
Published in Philosophical Magazine, 2023
Zohra Bahnes, Mohammed El Amine Monir, Ibtisam. F. Al-Maaitah, Amel Laref, Abdelkarim Bendoukha Reguig, Hadj Baltach, Djazia Nasri
Quaternary Heusler alloys have a cubic crystal structure corresponding to space group F3 m (no. 216) [14]; they crystallize in three different types of structure depending on the Wyckoff positions of the atoms, such as: Y-type (I), Y-type (II) and Y-type (III). It is shown in Table 1 how the atoms of the quaternary Heusler alloys CoX’YP (X’ = Co and Fe) can take different Wyckoff positions of the space group F3 m [13].