Influence of crystal fields on the magnetic properties of the rare-earth nitrides

Magnetic properties of ErN films

“…The critical field is about 0.2 T with a coercive field of 20 mT and there is a very small remanent magnetization of 0:2m B =Er 3 þ . The occurrence of a ferromagnetic ordering is accompanied by a nonsaturation of the magnetization at high field, as has been reported previously [10,11]. At 2 K, the magnetization in 6 T is only 5m B =Er 3 þ .…”

“…The spontaneous moment of 5:5m B in the ferromagnetic state is lower than m 0 , which has been attributed to an exchange interaction that is smaller in comparison to the crystal field splitting. Thus, saturation is not yet achieved under an applied field of 13 T ð7:9m B Þ [10,11]. Neutron diffraction experiments also reported a ferromagnetic ordering, characterized for HoN and ErN by a complicated non-collinear magnetic structure with successive ferromagnetic sheets perpendicular to ½1 1 1 [13].…”

“…Those data all agree that ErN is ferromagnetic, but with Curie temperatures that vary between 3.4 and 6 K. There is a rough agreement about the paramagnetic state: in the high temperature range ðT r 750 KÞ where the crystal field splitting is smaller than k B T, the susceptibility follows a Curie-Weiss law with a magnetic moment of 9:4m B ð 70:1Þ close to the free ion Er 3 þ value, m eff ðFIÞ ¼ g J ffiffiffiffiffiffiffiffiffiffiffiffiffiffi JðJ þ1Þ p m B ¼ 9:59m B . The paramagnetic Curie temperature y P varies from þ 4 K [10,11] to þ 14 K [12]. The spontaneous moment of 5:5m B in the ferromagnetic state is lower than m 0 , which has been attributed to an exchange interaction that is smaller in comparison to the crystal field splitting.…”

Semiconducting ground state ofGdNthin films

“…The most thoroughly studied of these is GdN, and although early studies produced conflicting results regarding the magnetic ordering, 3,4 GdN is now generally accepted to be ferromagnetic below about 70 K with a saturation moment of ϳ7 B / Gd. [5][6][7][8][9][10][11] More recently, advanced band structure calculations that take into account the magnetic order have predicted a range of electronic structures in the ferromagnetic ground state of GdN. Aerts et al, 12 using density functional theory in the local-spin-density approximation with a self-interaction correction, found that exchange splitting of the predominantly Gd s-d-like and N p-like conduction band states is sufficient to cause GdN to be halfmetallic, meaning that there are mobile electrons at the Fermi level of one spin only.…”

Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films

“…[1][2][3][4][5][6][7] However, the origin of magnetism in GdN is controversial. Recently, Duan et al 8 suggest that a next-nearest-neighbor antiferromagnetic superexchange interaction coexists along with RKKY nearestneighbor interaction.…”