Interplay between crystal and magnetic structures in YFe2(HαD1−α)4.2 compounds studied by neutron diffraction

Journal of Magnetism and Magnetic Materials

Isnard

Guillot

et al. 2019

Self Cite

The structural and magnetic properties of Y0.5Er0.5Fe2D4.2 deuteride have been investigated by continuous high field magnetic measurements up to 35 T and neutron powder diffraction experiments versus temperature and applied field. Y0.5Er0.5Fe2D4.2 crystallizes in a monoclinic structure (Pc space group) resulting from the deuterium order into 18 interstitial tetrahedral sites. At low field, the deuteride is ferrimagnetic (Ferri) up to 38 K, between 38 and 50 K, it undergoes a first order transition towards an antiferromagnetic (AFM) structure, which remains present up to TN=115 K. Upon applied field, two different types of metamagnetic behavior are observed depending on the temperature range. Below 38 K, a forced ferrimagneticferromagnetic (FM) transition is observed at a transition field BTrans of only 7 T (at 2 K), which is among the smallest encountered for Fe rich intermetallics. BTrans is not very sensitive to temperature changes nor to the Er content and its moderate value is explained by a deuterium induced weakening of the Er-Fe interaction. The second metamagnetic transition, observed between 38 and 150 K, from an AFM (Para) towards a FM structure, is related to the itinerant electron metamagnetic behavior of the Fe sublattice. BTrans increases linearly versus temperature with a dB/dT slope of 0.24±0.01 T.K-1. Above BTrans, Er moments parallel to the Fe moments are induced.

Section: Er1supporting

confidence: 89%

Section: High Temperature Metamagnetic Transition (T>38k)mentioning

confidence: 97%

Metamagnetic transitions in Y0.5Er0.5Fe2D4.2 deuteride studied by high magnetic field and neutron diffraction experiments

Journal of Magnetism and Magnetic Materials

Isnard

Guillot

et al. 2019

Self Cite

“…In other words, Ni atoms in the same block are ferromagnetically aligned while the magnetic coupling between adjacent blocks is antiferromagnetic (Table 1, figure 7). C14 hexagonal TiFe2, Hf0.825Ta0.175Fe2 and monoclinic YFe2H4.2 derived from a C15 cubic parent compound [52][53][54].…”

Section: Resultsmentioning

confidence: 99%

Relation between the weak itinerant magnetism inA₂Ni₇compounds (A = Y, La) and their stacked crystal structures

Crivello

J. Phys.: Condens. Matter

2020

The weak itinerant magnetic properties of A2Ni7 compounds with A = {Y, La} have been investigated using electronic band structure calculations in the relation with their polymorphic crystal structures. These compounds crystallizes in two structures resulting from the stacking of two and three blocks of [A2Ni4 + 2 ANi5] units for hexagonal 2H-La2Ni7 (Ce2Ni7 type) and rhombohedral 3R-Y2Ni7 (Gd2Co7 type) respectively. Experimentally, 2H-La2Ni7 is a weak itinerant antiferromagnet whereas 3R-Y2Ni7 is a weak itinerant ferromagnet. From the present first principles calculation within non-spin polarized state, both compounds present an electronic density of state with a sharp and narrow peak centered at the Fermi level corresponding to flat bands from 3d-Ni. This induces a magnetic instability and both compounds are more stable in a ferromagnetic (FM) order compared to a paramagnetic state (ΔE ≈ -35 meV/f.u.). The magnetic moment of each of the five Ni sites varies with their positions relative to the [A2Ni4] and [ANi5] units: they are minimum in the [A2Ni4] unit and maximum at the interface between two [ANi5] units. For 2H-La2Ni7, an antiferromagnetic (AFM) structure has been proposed and found with an energy comparable to that of the FM state. This AFM structure is described by two FM unit blocks of opposite Ni spin sign separated by a non-magnetic layer at z = 0 and ½. The Ni (2a) atoms belonging to this intermediate layer are located in the [La2Ni4] unit and are at a center of symmetry of the hexagonal cell (P63/mmc) where the resultant molecular field is cancelled. Further non-collinear spin calculations have been performed to determine the Ni moment orientations which are found preferentially parallel to the c axis for both FM and AFM structures.

“…Above TM = 50 K, a second type of metamagnetic behavior is observed for Y0.9Er0.1Fe2D4.2: the MT(B) curves shows again S-shape characteristic of a metamagnetic behavior, but their inflexion points are shifted to higher fields as the temperature increases. The previous NPD analysis for the deuterides with x = 0, 0.3 and 0.5 have shown that it corresponds to a transition from an AFM towards a FM state [73,77,78]. The transition fields (Btrans2), determined from the maximum of the MT(B) derivative, increases linearly versus temperature.…”

Section: Magnetic Propertiesmentioning

confidence: 93%

“…For an H (D) content of about 4.2 H(D)/f.u., these compounds crystallize in the same monoclinic structure as YFe2H4.2 and YFe2D4.2 [55]. This structure results from a distortion of the C15 cubic structure induced by hydrogen or deuterium order into specific tetrahedral interstitial sites (R2Fe2 and RFe3) [55,77]. The XRD patterns can be refined in a monoclinic structure with a C2/m space group as presented in Figure 1 for the hydride and deuteride of Y0.9Er0.1Fe2.…”

Section: Structural Propertiesmentioning

confidence: 97%

Origin of the metamagnetic transitions in Y1−Er Fe2(H,D)4.2 compounds

Journal of Magnetism and Magnetic Materials

Isnard

Shtender

et al. 2020

Self Cite

The structural and magnetic properties of Y1-xErxFe2 intermetallic compounds and their hydrides and deuterides Y1-xErxFe2H(D)4.2 have been investigated using X-ray diffraction and magnetic measurements under static and pulsed magnetic field up to 60 T. The intermetallics crystallize in the C15 cubic structure (Fd-3m space group), whereas corresponding hydrides and deuterides crystallize in a monoclinic structure (Pc space group). All compounds display a linear decrease of the unit cell volume versus Er concentration; the hydrides have a 0.8% larger cell volume compared to the deuterides with same Er content. They are ferrimagnetic at low field and temperature with a compensation point at x = 0.33 for the intermetallics and x = 0.57 for the hydrides and deuterides. A sharp first order ferromagnetic-antiferromagnetic (FM-AFM) transition is observed upon heating at TFM-AFM for both hydrides and deuterides. These compounds show two different types of field induced transitions, which have different physical origin. At low temperature (T < 50 K), a forced ferri-ferromagnetic metamagnetic transition with Btrans1  8 T, related to the change of the Er moments orientation from antiparallel to parallel Fe moment, is observed. Btrans1 is not sensitive to Er concentration, temperature and isotope effect. A second metamagnetic transition resulting from antiferromagnetic to ferrimagnetic state is also observed. The transition field Btrans2 increases linearly versus temperature and relates to the itinerant electron metamagnetic behavior of the Fe sublattice. An onset temperature TM0 is obtained by extrapolating TFM-AFM (B) at zero field. TM0 decreases linearly versus the Er content and is 45±5 K higher for the hydrides compared to the corresponding deuteride. The evolution of TM0 versus cell volume shows that it cannot be attributed exclusively to a pure volume effect and that electronic effects should also be considered.