Galvanomagnetic properties of Fe 2 YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys
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DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Galvanomagnetic Properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) Heusler Alloys N. I. Kourova*, V. V. Marchenkova,b,c, K. A. Belozerovaa, and H. W. Weberd a Institute
of Metal Physics, Ural Branch, Russian Academy of Sciences, ul. S. Kovalevskoi 18, Yekaterinburg, 620137 Russia b Ural Federal University, pr. Lenina 51, Yekaterinburg, 620002 Russia c International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw, 53-421 Poland d Atominstitut, Vienna University of Technology, Vienna, 1020 Austria *e-mail: [email protected] Received March 10, 2015
Abstract—The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R0) and anomalous (Rs) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant Rs in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (Rs ∝ ρ3.1 0 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe. DOI: 10.1134/S1063776115110047
1. INTRODUCTION X2YZ Heusler alloys, where X and Y are transition 3d metals and Z are the s and p elements of the third period of the periodic table, are of deep interest for practical application. So-called semimetallic ferromagnets (SMFs) are the most promising materials for magnetooptical data recording among these alloys. Modern spin density functional calculations of an electronic band structure (see, e.g., review [1]) show that their spectra have a wide (about 1 eV) energy gap at Fermi level EF in one of the subbands having different electron spin directions. Therefore, SMFs can be considered as “strong” band ferromagnets that are described by the “classical” Stoner theory [2]. Therefore X2YZ band ferromagnets attract particular scientific interest. These alloys are being extensively studied by exponential methods and theoretically. Most works deal with the investigation of the optical and magnetooptical properties of band ferromagnets, their magnetic and electrical properties, and ab initio band calculations. Information on the behavior of other electrical properties is also important. In particular, the galvanomagnetic properties of these alloys are still poorly understood.
2. EXPERIMENTAL In this work, we study the galvanomagnetic properties of some alloys of this class of band ferromagnets. Hall resistivity ρH(H) and electrical resistivity ρ(H) of Fe2YZ(Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) alloys were measured at liquid-helium
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