**5. Eu2O3 NPs-glass composite system: Smaller dielectric response and negative MD effect**

[38]. Since the current results suggest that MD behavior is probably a manifestation of magnetoresistance changes, depending on the NP size and separation. Enhancement of MD response (i.e., positive MD effect) through the decreases of NPs Er2O3 resistance under external magnetic field, (i.e., negative magnetoresistance) might imply the possible tunability of the

> 1.0 kHz 2.5 kHz 5.0 kHz 10.0 kHz 100.0 kHz

160 200 240 280 320

**Figure 10.** (Color online) (a) The (*ε*′-*T*) curves of Eu05-8 at different frequency, inset: representative plots of ln(*ε*'

 H = 0 T H = 5 T H = 9 T

2 3 4

ln(*T-Tm*)

Temperature (K)

4

8

e'

**Figure 11.** (Color online) (a), (b) The (*ε*′-*T*) curves of Eu05-7 and Eu05-9 measured under different applied magnetic

(b)

Eu05-9 *f***: 2.5 kHz**

12

 1.0 kHz 2.5 kHz 5.0 kHz 10.0 kHz 100.0 kHz

increasing frequency

160 200 240 280 320 360

Temperature (K)

<sup>−</sup><sup>1</sup> −*ε*' *m* −1 )

 H = 0 T H = 5 T H = 9 T

Eu05-7

H= 0 T

10

160 200 240 280 320 360

Temperature (K)

8

16

e'

24

Eu05-7

*f***: 2.5 kHz**

(a)

fields at a fixed frequency 2.5 kHz.

20

e'

30


vs ln(*T* −*Tm*) at temperatures higher than *Tm* for the Eu05-8 at different frequency values.

g = 1.58

ln(e*'-1*

e*'-1*

*m*)

resistive MD effect.

188 Ferroelectric Materials – Synthesis and Characterization

Typical data is shown for Eu2O3:SiO2 NPs-glass composite system having 0.5 mol% dopant Eu2O3 concentration calcined at different temperatures, namely, 700, 800 and 900o C (henceforth referred as Eu05-7, Eu05-8 and Eu05-9 respectively). Figure 10 represents the temperature dependence of *ε*′of Eu05-7 in the absence of the magnetic field. The nature of the variation of the (*ε*′-*T*) curves with maxima at *Tm* ∼ 270 K, represents as "diffuse phase transition" (DPT) around *Tm* with smaller *ε*′ than Er05-7 system, quite different and larger than that of bulk Eu2O3 [28] or pure SiO2 (∼ 3.9). Such system also follows a modified Curie–Weiss relationship [29], obtaining diffuseness exponent γ =1.58 (inset of Figure 10). The *ε*′-*T* plot (at 2.5 kHz), around the transition regime 240-320 K of Eu05-7 and Eu05-9 shows a decrease of *ε*′ under a magnetic field of 9 T (Figure 11). Here, we also observed particle size dependent effect, associated with DPT behavior as well as MD effect.
