Low-temperature phase transitions in the induced-moment systemPrB4

Abstract

We report the results of measurements of the electrical resistivity, the magnetization, and the specific heat of PrB 4 below room temperature. The crystal electric field ͑CEF͒ splits the 4f 2 multiplet of the Pr ions into nine singlets. In its ground state, PrB 4 is an induced-moment ferromagnet with a saturation magnetization as high as 2.1 B / ͑Pr ion͒. Contrary to previous experiments, we observe a first-order ferromagnetic to antiferromagnetic transition at T C Ϸ 15.9± 0.1 K with a latent heat ⌬Q = 8.6 J / mol. The antiferromagnetic long-range order is quenched above T N = 19.5 K. Susceptibility and specific heat data, as well as the enormous magnetic anisotropy, can quantitatively be reproduced by a mean-field calculation which takes into account the CEF, obtained from a point-charge model using effective charges obtained from a self-consistent electronic band-structure calculation and a Zeeman term, as well as an anisotropic dipolar magnetic exchange and an effective quadrupole-quadrupole interaction term.

Magnetotransport inNdB6single crystals

“…A large anomalous contribution to the Hall effect in the PM phase has also been observed in the parent compound EuB 6 . 25 In order to estimate R s below T N , we assume that the ordinary Hall coefficient does not vary with temperature. This is contrary to what has been argued in Ref.…”

Magnetic Properties and Negative Colossal Magnetoresistance of the Rare Earth Zintl phase EuIn2As2

“…Specifically, interactions between localized spins of magnetic rare earth cations and delocalized spins of mobile carriers result in interesting electro-magnetic phenomena, such as magnetoresistance (MR), which involves changes in the electrical resistivity of a material with changes in the magnitude of the applied magnetic field (H). Our previous studies on the transport properties of a family of alkaline earth and rare earth-containing magnetic Zintl phases having the Ca 14 AlSb 11 structure type, that is, A 14 MPn 11 (A = Sr, Ca, Ba, Yb, Eu; M = In, Mn; Pn = P, As, Sb, Bi), have indicated an intimate correlation between the onset of magnetic ordering events and changes in electrical resistivity, a feature which is typical of colossal magnetoresistant (CMR) materials, such as Eu x Ca 1− x B 6 − and the perovskite manganites. − Furthermore, CMR is generally associated with materials having a Fermi energy lying near a metal−insulator border, and the A 14 MPn 11 family of magnetoresistive materials range in their electrical behavior from semiconducting to metallic, dependent upon their composition, for example, Sr 14 MnAs 11 is a semiconductor and Sr 14 MnBi 11 is metallic. Interestingly in the A 14 MPn 11 compounds, the magnetically ordering cations are separated by a distance too large for direct coupling or superexchange, and the observation of both magnetic ordering and magnetoresistance is postulated to occur via a double exchange mechanism, ,− such as Rudderman−Kittel−Kasuya−Yosida (RKKY) coupling, where the local spins are communicated via delocalized carrier wave functions.…”

Solution of Macroscopic State Equations of Blume-Capel Model Using Nonlinear Dynamics Concepts

“…But in experiments, what is reduced to absolute zero is temperature itself. The important problem is to observe materials having interesting magnetic behavior near absolute zero [20,21]. Therefore we preferred using temperature instead of reduced temperature.…”