Microscopic theory of magnetic phase transitions inHoNi2B2C

Abstract

We present a microscopic theory for the low temperature metamagnetic phase diagram of HoNi 2 B 2 C that agrees well with experiments. For the same model we determined the zero field ground state as a function of temperature and find the c-axis commensurate to incommensurate transition in the expected temperature range. The complex behaviour of the system originates from the competition between the crystalline electric field and the RudermanKittel-Kasuya-Yosida interaction, whose effective form is obtained. No essential influence of superconductivity has to be invoked to understand the magnetic phase diagram of this material.

Torque magnetometry study of metamagnetic transitions in single-crystalHoNi2B2CatT≈1.9Rathnayaka1, Белевцев2, Naugle3 2007Phys. Rev. B4260View full textAdd to dashboardCite

“…This AFM phase is a c-axis modulated magnetic structure consisting of Ho-moments ferromagnetically aligned in the tetragonal basal (ab) planes along the [110] axis and stacked antiferromagnetically in the c-direction. The easy magnetic axis [110] was found experimentally and supported by theory [3,6,8,10,11]. In a tetragonal lattice four equivalent easy directions 110 are expected.…”

“…The choice of the subject was determined by its interest- * belevtsev@ilt.kharkov.ua † naugle@physics.tamu.edu ing magnetic properties, which cannot be considered as fully understood to date, and by the circumstance, that torque magnetometry was applied to the borocarbides so far only in limited cases [7,8]. The magnetic properties of HoNi 2 B 2 C, a superconductor with critical temperature T c ≈ 8.7 K, are characterized by (i) large anisotropy and (ii) availability of different field-induced magnetic phases at low temperatures [1,2,3,4,6,8,9,10,11,12]. Three magnetic transitions occur in a narrow temperature interval, when moving from the paramagnetic state in low field below T c ≈ 8.7 K. The first two transitions (at 6.0 K and 5.5 K) result in two incommensurate AFM phases, described in detail in [2,3,6].…”

Giant crystal-electric-field effect and complex magnetic behavior in single-crystallineCeRh3Si2

“…62-64 and references therein). Here again the crystalline electric field was taken into account to explain the complex magnetic phase diagram [65], yet the generalized ANNNI model (a kind of so-called clock model) was also successfully applied [66].…”

Magnetic phase diagram ofGdNi2B2C:Two-ion magnetoelasticity and anisotropic exchange coupling

“…1−8 Most of these states, in particular the modulated ones, are unstable against field and temperature variation, leading to a cascade of transformations 2,3,4 similar to the ones observed in the elemental rare-earths. It is the general opinion that the remarkable features observed in these H − T phase diagrams are governed by the combined influence of exchange couplings and crystalline electric field (CEF) interactions 9 : such an approach reproduced successfully the gross features of the magnetic H − T phase diagrams of HoNi 2 B 2 C. Nevertheless, various experimental observations suggest that two additional interactions, namely, anisotropic exchange interaction and magnetoelastic coupling, are necessary ingredients for the understanding of the behavior of the magnetic borocarbides. Magnetoelastic interactions are spectacularly manifested in the onset of a tetragonal-to-orthorhombic distortion at T N for R= Er, Ho, Dy, Tb compounds 10,11,12,13 , while the anisotropic exchange interactions were reported to be necessary for the description of the low-temperature magnetic properties of ErNi 2 B 2 C (Ref.…”