Q:

Trying to debunk a claim

Claim: Take any function $f(t) > 0$ for $t > 0$, such that $f(t) \to \infty$ as $t \to \infty$, then for $\sigma > 0$ $$|\zeta(\sigma + it)| = o(f(t))$$

Is there any already existing evidence, like papers or proofs or something that can debunk this?

As far as I know, under the Lindelof hypothesis
$$|\zeta(\frac{1}{2} + it)| = o(t^\epsilon)$$
and Littlewood has already proved that under the Riemann hypothesis
$$|\zeta(\frac{1}{2} + it)| = o\left(\exp\left(\frac{10\log t}{\log \log t}\right)\right)$$
both of which agree with the argument.
Also I know from this paper at http://arxiv.org/pdf/math/0612106v2.pdf that
$$\int_0^T |\zeta(1/2 + it)|^{2k}dt \gg_k T (\log T)^{k^2}$$
which kind of gives me a hint that there must be an obvious lower bound which can probably show that the condition given above for $\zeta(\sigma + it)$ and $f(t)$ is invalid.
Looking for references.

A:

First, your condition seems a bit strange to me. Since it seems to me it would imply that that the absolute value of $\zeta(1/2 + it)$ is bounded which would contradict the lower bound on the moments you recall. 
Yet, second, here is one (unconditional) result on $|\zeta(1/2 + it)|$ that gives some information you seem to seek (Jutila 1983, Bull LMS):
There exist positve constants $a,b,c$ such that for each $T\ge 10$ one has
$$ \exp( a(\log \log T)^{1/2}) \le |\zeta(1/2 + it)| \le \exp ( b(\log \log T)^{1/2})$$
for $t$ in a subset of $[0,T]$ of measure at least $cT$.

A:

Read Theorem 8.12 in Titchmarsh:
For $\frac12 \le \sigma <1$  take $0<\alpha <1-\sigma$. Then the inequality 
$|\zeta(\sigma+it)| > \exp(\log^\alpha t)$ is satisfied for indefinitely
large values of $t$.
Therefore  $f(t)=\exp(\log^\alpha t)$ does not satisfy your assertion for this $\sigma$
.

