A substantial increase of Curie temperature in a new type of diluted magnetic semiconductors via effects of chemical pressure

Abstract

Chemical pressure is an effective method to tune physical properties, particularly for diluted magnetic semiconductors (DMS) of which ferromagnetic ordering is mediated by charge carriers. Via substitution of smaller Ca for larger Sr, we introduce chemical pressure on (Sr,Na)(Cd,Mn) 2 As 2 to fabricate a new DMS material (Ca,Na)(Cd,Mn) 2 As 2 . Carriers and spins are introduced by substitutions of (Ca,Na) and (Cd,Mn) respectively. The unit cell volume reduces by 6.2% after complete substitution of Ca for Sr, suggesting a subsistent chemical pressure. Importantly the local geometry of [Cd/MnAs 4 ] tetrahedron is optimized via chemical compression that increases the Mn-As hybridization leading to enhanced ferromagnetic interactions. As a result, the maximum Curie temperature (T C ) is increased by about 50% while the the maximum saturation moment increases by over 100% from (Sr,Na)(Cd,Mn) 2 As 2 to (Ca,Na)(Cd,Mn) 2 As 2 . The chemical pressure estimated from the equation of state is equal to an external physical pressure of 3.6 GPa.

Room temperature intrinsic diluted magnetic semiconductor Li(Cd,Mn)As

“…4(a) shows the temperature-dependent resistivity of Li 1.04 (Cd 1Àx Mn x )As samples with x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, and 0.15. The resistivity of parent compound LiCdAs increases with decreasing temperature, which exhibits a typical semiconductor behavior 39 and is consistent with the previous report. 25 The resistivity of the doped samples also increases monotonically with the decrease in temperature at various doping concentrations.…”

Drastic improvement of Curie temperature by chemical pressure in N-type diluted magnetic semiconductor Ba(Zn,Co)$$_{2}$$As$$_{2}$$

“…This is opposite to the case observed in (Ba,K)(Zn,Mn) As , where positive chemical pressure induced by P/As substitution suppress the 25 . Previous results have shown that long-range ferromagnetic interaction in many p -type DMSs is predominantly mediated by the itinerant carries 26 , 27 , 35 – 39 . In p -type (Ba,K)(Zn,Mn) As , the long-range magnetic ordering is mediated by the p states of As through As 4 p -Mn 3 d hybridization.…”

“…While in contrast, the resistivity of Sr-doped sample is lower than that of Ba(Zn Co ) As in most temperature range. This can be attribute to the broadened electronic bandwidth and increased carrier mobility with compression of the lattice 26 , 35 . To examine whether the type of carriers for Sr-doped samples with iso-valent doping has been changed, we measured Hall effect.…”

(Ca,K)(Zn,Mn)2As2: Ferromagnetic semiconductor induced by decoupled charge and spin doping in CaZn2As2

“…Theoretically, this probability will increase drastically with increasing x, which enhances the direct antiferromagnetic coupling interaction between Mn-Mn pairs. We notice that with this interaction, 100% Mn doped Ca(Zn 1−x Mn x ) 2 As 2 , CaMn 2 As 2 , becomes an antiferromagnet with Neel temperature ~ 62 K [34] .…”